sgi-xpc: prevent false heartbeat failures

[~andy/linux] / drivers / misc / sgi-xp / xpc_sn2.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2008-2009 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * Cross Partition Communication (XPC) sn2-based functions.
 *
 *     Architecture specific implementation of common functions.
 *
 */

#include <linux/delay.h>
#include <asm/uncached.h>
#include <asm/sn/mspec.h>
#include <asm/sn/sn_sal.h>
#include "xpc.h"

/*
 * Define the number of u64s required to represent all the C-brick nasids
 * as a bitmap.  The cross-partition kernel modules deal only with
 * C-brick nasids, thus the need for bitmaps which don't account for
 * odd-numbered (non C-brick) nasids.
 */
#define XPC_MAX_PHYSNODES_SN2   (MAX_NUMALINK_NODES / 2)
#define XP_NASID_MASK_BYTES_SN2 ((XPC_MAX_PHYSNODES_SN2 + 7) / 8)
#define XP_NASID_MASK_WORDS_SN2 ((XPC_MAX_PHYSNODES_SN2 + 63) / 64)

/*
 * Memory for XPC's amo variables is allocated by the MSPEC driver. These
 * pages are located in the lowest granule. The lowest granule uses 4k pages
 * for cached references and an alternate TLB handler to never provide a
 * cacheable mapping for the entire region. This will prevent speculative
 * reading of cached copies of our lines from being issued which will cause
 * a PI FSB Protocol error to be generated by the SHUB. For XPC, we need 64
 * amo variables (based on XP_MAX_NPARTITIONS_SN2) to identify the senders of
 * NOTIFY IRQs, 128 amo variables (based on XP_NASID_MASK_WORDS_SN2) to identify
 * the senders of ACTIVATE IRQs, 1 amo variable to identify which remote
 * partitions (i.e., XPCs) consider themselves currently engaged with the
 * local XPC and 1 amo variable to request partition deactivation.
 */
#define XPC_NOTIFY_IRQ_AMOS_SN2         0
#define XPC_ACTIVATE_IRQ_AMOS_SN2       (XPC_NOTIFY_IRQ_AMOS_SN2 + \
                                         XP_MAX_NPARTITIONS_SN2)
#define XPC_ENGAGED_PARTITIONS_AMO_SN2  (XPC_ACTIVATE_IRQ_AMOS_SN2 + \
                                         XP_NASID_MASK_WORDS_SN2)
#define XPC_DEACTIVATE_REQUEST_AMO_SN2  (XPC_ENGAGED_PARTITIONS_AMO_SN2 + 1)

/*
 * Buffer used to store a local copy of portions of a remote partition's
 * reserved page (either its header and part_nasids mask, or its vars).
 */
static void *xpc_remote_copy_buffer_base_sn2;
static char *xpc_remote_copy_buffer_sn2;

static struct xpc_vars_sn2 *xpc_vars_sn2;
static struct xpc_vars_part_sn2 *xpc_vars_part_sn2;

static int
xpc_setup_partitions_sn_sn2(void)
{
        /* nothing needs to be done */
        return 0;
}

static void
xpc_teardown_partitions_sn_sn2(void)
{
        /* nothing needs to be done */
}

/* SH_IPI_ACCESS shub register value on startup */
static u64 xpc_sh1_IPI_access_sn2;
static u64 xpc_sh2_IPI_access0_sn2;
static u64 xpc_sh2_IPI_access1_sn2;
static u64 xpc_sh2_IPI_access2_sn2;
static u64 xpc_sh2_IPI_access3_sn2;

/*
 * Change protections to allow IPI operations.
 */
static void
xpc_allow_IPI_ops_sn2(void)
{
        int node;
        int nasid;

        /* !!! The following should get moved into SAL. */
        if (is_shub2()) {
                xpc_sh2_IPI_access0_sn2 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS0));
                xpc_sh2_IPI_access1_sn2 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS1));
                xpc_sh2_IPI_access2_sn2 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS2));
                xpc_sh2_IPI_access3_sn2 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS3));

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                              -1UL);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                              -1UL);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                              -1UL);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                              -1UL);
                }
        } else {
                xpc_sh1_IPI_access_sn2 =
                    (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH1_IPI_ACCESS));

                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                              -1UL);
                }
        }
}

/*
 * Restrict protections to disallow IPI operations.
 */
static void
xpc_disallow_IPI_ops_sn2(void)
{
        int node;
        int nasid;

        /* !!! The following should get moved into SAL. */
        if (is_shub2()) {
                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                              xpc_sh2_IPI_access0_sn2);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                              xpc_sh2_IPI_access1_sn2);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                              xpc_sh2_IPI_access2_sn2);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                              xpc_sh2_IPI_access3_sn2);
                }
        } else {
                for_each_online_node(node) {
                        nasid = cnodeid_to_nasid(node);
                        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                              xpc_sh1_IPI_access_sn2);
                }
        }
}

/*
 * The following set of functions are used for the sending and receiving of
 * IRQs (also known as IPIs). There are two flavors of IRQs, one that is
 * associated with partition activity (SGI_XPC_ACTIVATE) and the other that
 * is associated with channel activity (SGI_XPC_NOTIFY).
 */

static u64
xpc_receive_IRQ_amo_sn2(struct amo *amo)
{
        return FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_CLEAR);
}

static enum xp_retval
xpc_send_IRQ_sn2(struct amo *amo, u64 flag, int nasid, int phys_cpuid,
                 int vector)
{
        int ret = 0;
        unsigned long irq_flags;

        local_irq_save(irq_flags);

        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR, flag);
        sn_send_IPI_phys(nasid, phys_cpuid, vector, 0);

        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IRQs and amos to it until the heartbeat times out.
         */
        ret = xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);

        return (ret == 0) ? xpSuccess : xpPioReadError;
}

static struct amo *
xpc_init_IRQ_amo_sn2(int index)
{
        struct amo *amo = xpc_vars_sn2->amos_page + index;

        (void)xpc_receive_IRQ_amo_sn2(amo);     /* clear amo variable */
        return amo;
}

/*
 * Functions associated with SGI_XPC_ACTIVATE IRQ.
 */

/*
 * Notify the heartbeat check thread that an activate IRQ has been received.
 */
static irqreturn_t
xpc_handle_activate_IRQ_sn2(int irq, void *dev_id)
{
        unsigned long irq_flags;

        spin_lock_irqsave(&xpc_activate_IRQ_rcvd_lock, irq_flags);
        xpc_activate_IRQ_rcvd++;
        spin_unlock_irqrestore(&xpc_activate_IRQ_rcvd_lock, irq_flags);

        wake_up_interruptible(&xpc_activate_IRQ_wq);
        return IRQ_HANDLED;
}

/*
 * Flag the appropriate amo variable and send an IRQ to the specified node.
 */
static void
xpc_send_activate_IRQ_sn2(unsigned long amos_page_pa, int from_nasid,
                          int to_nasid, int to_phys_cpuid)
{
        struct amo *amos = (struct amo *)__va(amos_page_pa +
                                              (XPC_ACTIVATE_IRQ_AMOS_SN2 *
                                              sizeof(struct amo)));

        (void)xpc_send_IRQ_sn2(&amos[BIT_WORD(from_nasid / 2)],
                               BIT_MASK(from_nasid / 2), to_nasid,
                               to_phys_cpuid, SGI_XPC_ACTIVATE);
}

static void
xpc_send_local_activate_IRQ_sn2(int from_nasid)
{
        unsigned long irq_flags;
        struct amo *amos = (struct amo *)__va(xpc_vars_sn2->amos_page_pa +
                                              (XPC_ACTIVATE_IRQ_AMOS_SN2 *
                                              sizeof(struct amo)));

        /* fake the sending and receipt of an activate IRQ from remote nasid */
        FETCHOP_STORE_OP(TO_AMO((u64)&amos[BIT_WORD(from_nasid / 2)].variable),
                         FETCHOP_OR, BIT_MASK(from_nasid / 2));

        spin_lock_irqsave(&xpc_activate_IRQ_rcvd_lock, irq_flags);
        xpc_activate_IRQ_rcvd++;
        spin_unlock_irqrestore(&xpc_activate_IRQ_rcvd_lock, irq_flags);

        wake_up_interruptible(&xpc_activate_IRQ_wq);
}

/*
 * Functions associated with SGI_XPC_NOTIFY IRQ.
 */

/*
 * Check to see if any chctl flags were sent from the specified partition.
 */
static void
xpc_check_for_sent_chctl_flags_sn2(struct xpc_partition *part)
{
        union xpc_channel_ctl_flags chctl;
        unsigned long irq_flags;

        chctl.all_flags = xpc_receive_IRQ_amo_sn2(part->sn.sn2.
                                                  local_chctl_amo_va);
        if (chctl.all_flags == 0)
                return;

        spin_lock_irqsave(&part->chctl_lock, irq_flags);
        part->chctl.all_flags |= chctl.all_flags;
        spin_unlock_irqrestore(&part->chctl_lock, irq_flags);

        dev_dbg(xpc_chan, "received notify IRQ from partid=%d, chctl.all_flags="
                "0x%lx\n", XPC_PARTID(part), chctl.all_flags);

        xpc_wakeup_channel_mgr(part);
}

/*
 * Handle the receipt of a SGI_XPC_NOTIFY IRQ by seeing whether the specified
 * partition actually sent it. Since SGI_XPC_NOTIFY IRQs may be shared by more
 * than one partition, we use an amo structure per partition to indicate
 * whether a partition has sent an IRQ or not.  If it has, then wake up the
 * associated kthread to handle it.
 *
 * All SGI_XPC_NOTIFY IRQs received by XPC are the result of IRQs sent by XPC
 * running on other partitions.
 *
 * Noteworthy Arguments:
 *
 *      irq - Interrupt ReQuest number. NOT USED.
 *
 *      dev_id - partid of IRQ's potential sender.
 */
static irqreturn_t
xpc_handle_notify_IRQ_sn2(int irq, void *dev_id)
{
        short partid = (short)(u64)dev_id;
        struct xpc_partition *part = &xpc_partitions[partid];

        DBUG_ON(partid < 0 || partid >= XP_MAX_NPARTITIONS_SN2);

        if (xpc_part_ref(part)) {
                xpc_check_for_sent_chctl_flags_sn2(part);

                xpc_part_deref(part);
        }
        return IRQ_HANDLED;
}

/*
 * Check to see if xpc_handle_notify_IRQ_sn2() dropped any IRQs on the floor
 * because the write to their associated amo variable completed after the IRQ
 * was received.
 */
static void
xpc_check_for_dropped_notify_IRQ_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;

        if (xpc_part_ref(part)) {
                xpc_check_for_sent_chctl_flags_sn2(part);

                part_sn2->dropped_notify_IRQ_timer.expires = jiffies +
                    XPC_DROPPED_NOTIFY_IRQ_WAIT_INTERVAL;
                add_timer(&part_sn2->dropped_notify_IRQ_timer);
                xpc_part_deref(part);
        }
}

/*
 * Send a notify IRQ to the remote partition that is associated with the
 * specified channel.
 */
static void
xpc_send_notify_IRQ_sn2(struct xpc_channel *ch, u8 chctl_flag,
                        char *chctl_flag_string, unsigned long *irq_flags)
{
        struct xpc_partition *part = &xpc_partitions[ch->partid];
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        union xpc_channel_ctl_flags chctl = { 0 };
        enum xp_retval ret;

        if (likely(part->act_state != XPC_P_AS_DEACTIVATING)) {
                chctl.flags[ch->number] = chctl_flag;
                ret = xpc_send_IRQ_sn2(part_sn2->remote_chctl_amo_va,
                                       chctl.all_flags,
                                       part_sn2->notify_IRQ_nasid,
                                       part_sn2->notify_IRQ_phys_cpuid,
                                       SGI_XPC_NOTIFY);
                dev_dbg(xpc_chan, "%s sent to partid=%d, channel=%d, ret=%d\n",
                        chctl_flag_string, ch->partid, ch->number, ret);
                if (unlikely(ret != xpSuccess)) {
                        if (irq_flags != NULL)
                                spin_unlock_irqrestore(&ch->lock, *irq_flags);
                        XPC_DEACTIVATE_PARTITION(part, ret);
                        if (irq_flags != NULL)
                                spin_lock_irqsave(&ch->lock, *irq_flags);
                }
        }
}

#define XPC_SEND_NOTIFY_IRQ_SN2(_ch, _ipi_f, _irq_f) \
                xpc_send_notify_IRQ_sn2(_ch, _ipi_f, #_ipi_f, _irq_f)

/*
 * Make it look like the remote partition, which is associated with the
 * specified channel, sent us a notify IRQ. This faked IRQ will be handled
 * by xpc_check_for_dropped_notify_IRQ_sn2().
 */
static void
xpc_send_local_notify_IRQ_sn2(struct xpc_channel *ch, u8 chctl_flag,
                              char *chctl_flag_string)
{
        struct xpc_partition *part = &xpc_partitions[ch->partid];
        union xpc_channel_ctl_flags chctl = { 0 };

        chctl.flags[ch->number] = chctl_flag;
        FETCHOP_STORE_OP(TO_AMO((u64)&part->sn.sn2.local_chctl_amo_va->
                                variable), FETCHOP_OR, chctl.all_flags);
        dev_dbg(xpc_chan, "%s sent local from partid=%d, channel=%d\n",
                chctl_flag_string, ch->partid, ch->number);
}

#define XPC_SEND_LOCAL_NOTIFY_IRQ_SN2(_ch, _ipi_f) \
                xpc_send_local_notify_IRQ_sn2(_ch, _ipi_f, #_ipi_f)

static void
xpc_send_chctl_closerequest_sn2(struct xpc_channel *ch,
                                unsigned long *irq_flags)
{
        struct xpc_openclose_args *args = ch->sn.sn2.local_openclose_args;

        args->reason = ch->reason;
        XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_CLOSEREQUEST, irq_flags);
}

static void
xpc_send_chctl_closereply_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
        XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_CLOSEREPLY, irq_flags);
}

static void
xpc_send_chctl_openrequest_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
        struct xpc_openclose_args *args = ch->sn.sn2.local_openclose_args;

        args->entry_size = ch->entry_size;
        args->local_nentries = ch->local_nentries;
        XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_OPENREQUEST, irq_flags);
}

static void
xpc_send_chctl_openreply_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
        struct xpc_openclose_args *args = ch->sn.sn2.local_openclose_args;

        args->remote_nentries = ch->remote_nentries;
        args->local_nentries = ch->local_nentries;
        args->local_msgqueue_pa = xp_pa(ch->sn.sn2.local_msgqueue);
        XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_OPENREPLY, irq_flags);
}

static void
xpc_send_chctl_msgrequest_sn2(struct xpc_channel *ch)
{
        XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_MSGREQUEST, NULL);
}

static void
xpc_send_chctl_local_msgrequest_sn2(struct xpc_channel *ch)
{
        XPC_SEND_LOCAL_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_MSGREQUEST);
}

static enum xp_retval
xpc_save_remote_msgqueue_pa_sn2(struct xpc_channel *ch,
                                unsigned long msgqueue_pa)
{
        ch->sn.sn2.remote_msgqueue_pa = msgqueue_pa;
        return xpSuccess;
}

/*
 * This next set of functions are used to keep track of when a partition is
 * potentially engaged in accessing memory belonging to another partition.
 */

static void
xpc_indicate_partition_engaged_sn2(struct xpc_partition *part)
{
        unsigned long irq_flags;
        struct amo *amo = (struct amo *)__va(part->sn.sn2.remote_amos_page_pa +
                                             (XPC_ENGAGED_PARTITIONS_AMO_SN2 *
                                             sizeof(struct amo)));

        local_irq_save(irq_flags);

        /* set bit corresponding to our partid in remote partition's amo */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR,
                         BIT(sn_partition_id));

        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IRQs and amos to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);
}

static void
xpc_indicate_partition_disengaged_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        unsigned long irq_flags;
        struct amo *amo = (struct amo *)__va(part_sn2->remote_amos_page_pa +
                                             (XPC_ENGAGED_PARTITIONS_AMO_SN2 *
                                             sizeof(struct amo)));

        local_irq_save(irq_flags);

        /* clear bit corresponding to our partid in remote partition's amo */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
                         ~BIT(sn_partition_id));

        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IRQs and amos to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);

        /*
         * Send activate IRQ to get other side to see that we've cleared our
         * bit in their engaged partitions amo.
         */
        xpc_send_activate_IRQ_sn2(part_sn2->remote_amos_page_pa,
                                  cnodeid_to_nasid(0),
                                  part_sn2->activate_IRQ_nasid,
                                  part_sn2->activate_IRQ_phys_cpuid);
}

static void
xpc_assume_partition_disengaged_sn2(short partid)
{
        struct amo *amo = xpc_vars_sn2->amos_page +
                          XPC_ENGAGED_PARTITIONS_AMO_SN2;

        /* clear bit(s) based on partid mask in our partition's amo */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
                         ~BIT(partid));
}

static int
xpc_partition_engaged_sn2(short partid)
{
        struct amo *amo = xpc_vars_sn2->amos_page +
                          XPC_ENGAGED_PARTITIONS_AMO_SN2;

        /* our partition's amo variable ANDed with partid mask */
        return (FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) &
                BIT(partid)) != 0;
}

static int
xpc_any_partition_engaged_sn2(void)
{
        struct amo *amo = xpc_vars_sn2->amos_page +
                          XPC_ENGAGED_PARTITIONS_AMO_SN2;

        /* our partition's amo variable */
        return FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) != 0;
}

/* original protection values for each node */
static u64 xpc_prot_vec_sn2[MAX_NUMNODES];

/*
 * Change protections to allow amo operations on non-Shub 1.1 systems.
 */
static enum xp_retval
xpc_allow_amo_ops_sn2(struct amo *amos_page)
{
        enum xp_retval ret = xpSuccess;

        /*
         * On SHUB 1.1, we cannot call sn_change_memprotect() since the BIST
         * collides with memory operations. On those systems we call
         * xpc_allow_amo_ops_shub_wars_1_1_sn2() instead.
         */
        if (!enable_shub_wars_1_1())
                ret = xp_expand_memprotect(ia64_tpa((u64)amos_page), PAGE_SIZE);

        return ret;
}

/*
 * Change protections to allow amo operations on Shub 1.1 systems.
 */
static void
xpc_allow_amo_ops_shub_wars_1_1_sn2(void)
{
        int node;
        int nasid;

        if (!enable_shub_wars_1_1())
                return;

        for_each_online_node(node) {
                nasid = cnodeid_to_nasid(node);
                /* save current protection values */
                xpc_prot_vec_sn2[node] =
                    (u64)HUB_L((u64 *)GLOBAL_MMR_ADDR(nasid,
                                                  SH1_MD_DQLP_MMR_DIR_PRIVEC0));
                /* open up everything */
                HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid,
                                             SH1_MD_DQLP_MMR_DIR_PRIVEC0),
                      -1UL);
                HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid,
                                             SH1_MD_DQRP_MMR_DIR_PRIVEC0),
                      -1UL);
        }
}

static enum xp_retval
xpc_get_partition_rsvd_page_pa_sn2(void *buf, u64 *cookie, unsigned long *rp_pa,
                                   size_t *len)
{
        s64 status;
        enum xp_retval ret;

        status = sn_partition_reserved_page_pa((u64)buf, cookie, rp_pa, len);
        if (status == SALRET_OK)
                ret = xpSuccess;
        else if (status == SALRET_MORE_PASSES)
                ret = xpNeedMoreInfo;
        else
                ret = xpSalError;

        return ret;
}


static int
xpc_setup_rsvd_page_sn_sn2(struct xpc_rsvd_page *rp)
{
        struct amo *amos_page;
        int i;
        int ret;

        xpc_vars_sn2 = XPC_RP_VARS(rp);

        rp->sn.sn2.vars_pa = xp_pa(xpc_vars_sn2);

        /* vars_part array follows immediately after vars */
        xpc_vars_part_sn2 = (struct xpc_vars_part_sn2 *)((u8 *)XPC_RP_VARS(rp) +
                                                         XPC_RP_VARS_SIZE);

        /*
         * Before clearing xpc_vars_sn2, see if a page of amos had been
         * previously allocated. If not we'll need to allocate one and set
         * permissions so that cross-partition amos are allowed.
         *
         * The allocated amo page needs MCA reporting to remain disabled after
         * XPC has unloaded.  To make this work, we keep a copy of the pointer
         * to this page (i.e., amos_page) in the struct xpc_vars_sn2 structure,
         * which is pointed to by the reserved page, and re-use that saved copy
         * on subsequent loads of XPC. This amo page is never freed, and its
         * memory protections are never restricted.
         */
        amos_page = xpc_vars_sn2->amos_page;
        if (amos_page == NULL) {
                amos_page = (struct amo *)TO_AMO(uncached_alloc_page(0, 1));
                if (amos_page == NULL) {
                        dev_err(xpc_part, "can't allocate page of amos\n");
                        return -ENOMEM;
                }

                /*
                 * Open up amo-R/W to cpu.  This is done on Shub 1.1 systems
                 * when xpc_allow_amo_ops_shub_wars_1_1_sn2() is called.
                 */
                ret = xpc_allow_amo_ops_sn2(amos_page);
                if (ret != xpSuccess) {
                        dev_err(xpc_part, "can't allow amo operations\n");
                        uncached_free_page(__IA64_UNCACHED_OFFSET |
                                           TO_PHYS((u64)amos_page), 1);
                        return -EPERM;
                }
        }

        /* clear xpc_vars_sn2 */
        memset(xpc_vars_sn2, 0, sizeof(struct xpc_vars_sn2));

        xpc_vars_sn2->version = XPC_V_VERSION;
        xpc_vars_sn2->activate_IRQ_nasid = cpuid_to_nasid(0);
        xpc_vars_sn2->activate_IRQ_phys_cpuid = cpu_physical_id(0);
        xpc_vars_sn2->vars_part_pa = xp_pa(xpc_vars_part_sn2);
        xpc_vars_sn2->amos_page_pa = ia64_tpa((u64)amos_page);
        xpc_vars_sn2->amos_page = amos_page;    /* save for next load of XPC */

        /* clear xpc_vars_part_sn2 */
        memset((u64 *)xpc_vars_part_sn2, 0, sizeof(struct xpc_vars_part_sn2) *
               XP_MAX_NPARTITIONS_SN2);

        /* initialize the activate IRQ related amo variables */
        for (i = 0; i < xpc_nasid_mask_nlongs; i++)
                (void)xpc_init_IRQ_amo_sn2(XPC_ACTIVATE_IRQ_AMOS_SN2 + i);

        /* initialize the engaged remote partitions related amo variables */
        (void)xpc_init_IRQ_amo_sn2(XPC_ENGAGED_PARTITIONS_AMO_SN2);
        (void)xpc_init_IRQ_amo_sn2(XPC_DEACTIVATE_REQUEST_AMO_SN2);

        return 0;
}

static int
xpc_hb_allowed_sn2(short partid, void *heartbeating_to_mask)
{
        return test_bit(partid, heartbeating_to_mask);
}

static void
xpc_allow_hb_sn2(short partid)
{
        DBUG_ON(xpc_vars_sn2 == NULL);
        set_bit(partid, xpc_vars_sn2->heartbeating_to_mask);
}

static void
xpc_disallow_hb_sn2(short partid)
{
        DBUG_ON(xpc_vars_sn2 == NULL);
        clear_bit(partid, xpc_vars_sn2->heartbeating_to_mask);
}

static void
xpc_disallow_all_hbs_sn2(void)
{
        DBUG_ON(xpc_vars_sn2 == NULL);
        bitmap_zero(xpc_vars_sn2->heartbeating_to_mask, xp_max_npartitions);
}

static void
xpc_increment_heartbeat_sn2(void)
{
        xpc_vars_sn2->heartbeat++;
}

static void
xpc_offline_heartbeat_sn2(void)
{
        xpc_increment_heartbeat_sn2();
        xpc_vars_sn2->heartbeat_offline = 1;
}

static void
xpc_online_heartbeat_sn2(void)
{
        xpc_increment_heartbeat_sn2();
        xpc_vars_sn2->heartbeat_offline = 0;
}

static void
xpc_heartbeat_init_sn2(void)
{
        DBUG_ON(xpc_vars_sn2 == NULL);

        bitmap_zero(xpc_vars_sn2->heartbeating_to_mask, XP_MAX_NPARTITIONS_SN2);
        xpc_online_heartbeat_sn2();
}

static void
xpc_heartbeat_exit_sn2(void)
{
        xpc_offline_heartbeat_sn2();
}

static enum xp_retval
xpc_get_remote_heartbeat_sn2(struct xpc_partition *part)
{
        struct xpc_vars_sn2 *remote_vars;
        enum xp_retval ret;

        remote_vars = (struct xpc_vars_sn2 *)xpc_remote_copy_buffer_sn2;

        /* pull the remote vars structure that contains the heartbeat */
        ret = xp_remote_memcpy(xp_pa(remote_vars),
                               part->sn.sn2.remote_vars_pa,
                               XPC_RP_VARS_SIZE);
        if (ret != xpSuccess)
                return ret;

        dev_dbg(xpc_part, "partid=%d, heartbeat=%ld, last_heartbeat=%ld, "
                "heartbeat_offline=%ld, HB_mask[0]=0x%lx\n", XPC_PARTID(part),
                remote_vars->heartbeat, part->last_heartbeat,
                remote_vars->heartbeat_offline,
                remote_vars->heartbeating_to_mask[0]);

        if ((remote_vars->heartbeat == part->last_heartbeat &&
            !remote_vars->heartbeat_offline) ||
            !xpc_hb_allowed_sn2(sn_partition_id,
                                remote_vars->heartbeating_to_mask)) {
                ret = xpNoHeartbeat;
        } else {
                part->last_heartbeat = remote_vars->heartbeat;
        }

        return ret;
}

/*
 * Get a copy of the remote partition's XPC variables from the reserved page.
 *
 * remote_vars points to a buffer that is cacheline aligned for BTE copies and
 * assumed to be of size XPC_RP_VARS_SIZE.
 */
static enum xp_retval
xpc_get_remote_vars_sn2(unsigned long remote_vars_pa,
                        struct xpc_vars_sn2 *remote_vars)
{
        enum xp_retval ret;

        if (remote_vars_pa == 0)
                return xpVarsNotSet;

        /* pull over the cross partition variables */
        ret = xp_remote_memcpy(xp_pa(remote_vars), remote_vars_pa,
                               XPC_RP_VARS_SIZE);
        if (ret != xpSuccess)
                return ret;

        if (XPC_VERSION_MAJOR(remote_vars->version) !=
            XPC_VERSION_MAJOR(XPC_V_VERSION)) {
                return xpBadVersion;
        }

        return xpSuccess;
}

static void
xpc_request_partition_activation_sn2(struct xpc_rsvd_page *remote_rp,
                                     unsigned long remote_rp_pa, int nasid)
{
        xpc_send_local_activate_IRQ_sn2(nasid);
}

static void
xpc_request_partition_reactivation_sn2(struct xpc_partition *part)
{
        xpc_send_local_activate_IRQ_sn2(part->sn.sn2.activate_IRQ_nasid);
}

static void
xpc_request_partition_deactivation_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        unsigned long irq_flags;
        struct amo *amo = (struct amo *)__va(part_sn2->remote_amos_page_pa +
                                             (XPC_DEACTIVATE_REQUEST_AMO_SN2 *
                                             sizeof(struct amo)));

        local_irq_save(irq_flags);

        /* set bit corresponding to our partid in remote partition's amo */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR,
                         BIT(sn_partition_id));

        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IRQs and amos to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);

        /*
         * Send activate IRQ to get other side to see that we've set our
         * bit in their deactivate request amo.
         */
        xpc_send_activate_IRQ_sn2(part_sn2->remote_amos_page_pa,
                                  cnodeid_to_nasid(0),
                                  part_sn2->activate_IRQ_nasid,
                                  part_sn2->activate_IRQ_phys_cpuid);
}

static void
xpc_cancel_partition_deactivation_request_sn2(struct xpc_partition *part)
{
        unsigned long irq_flags;
        struct amo *amo = (struct amo *)__va(part->sn.sn2.remote_amos_page_pa +
                                             (XPC_DEACTIVATE_REQUEST_AMO_SN2 *
                                             sizeof(struct amo)));

        local_irq_save(irq_flags);

        /* clear bit corresponding to our partid in remote partition's amo */
        FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
                         ~BIT(sn_partition_id));

        /*
         * We must always use the nofault function regardless of whether we
         * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
         * didn't, we'd never know that the other partition is down and would
         * keep sending IRQs and amos to it until the heartbeat times out.
         */
        (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                                               variable),
                                                     xp_nofault_PIOR_target));

        local_irq_restore(irq_flags);
}

static int
xpc_partition_deactivation_requested_sn2(short partid)
{
        struct amo *amo = xpc_vars_sn2->amos_page +
                          XPC_DEACTIVATE_REQUEST_AMO_SN2;

        /* our partition's amo variable ANDed with partid mask */
        return (FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) &
                BIT(partid)) != 0;
}

/*
 * Update the remote partition's info.
 */
static void
xpc_update_partition_info_sn2(struct xpc_partition *part, u8 remote_rp_version,
                              unsigned long *remote_rp_ts_jiffies,
                              unsigned long remote_rp_pa,
                              unsigned long remote_vars_pa,
                              struct xpc_vars_sn2 *remote_vars)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;

        part->remote_rp_version = remote_rp_version;
        dev_dbg(xpc_part, "  remote_rp_version = 0x%016x\n",
                part->remote_rp_version);

        part->remote_rp_ts_jiffies = *remote_rp_ts_jiffies;
        dev_dbg(xpc_part, "  remote_rp_ts_jiffies = 0x%016lx\n",
                part->remote_rp_ts_jiffies);

        part->remote_rp_pa = remote_rp_pa;
        dev_dbg(xpc_part, "  remote_rp_pa = 0x%016lx\n", part->remote_rp_pa);

        part_sn2->remote_vars_pa = remote_vars_pa;
        dev_dbg(xpc_part, "  remote_vars_pa = 0x%016lx\n",
                part_sn2->remote_vars_pa);

        part->last_heartbeat = remote_vars->heartbeat - 1;
        dev_dbg(xpc_part, "  last_heartbeat = 0x%016lx\n",
                part->last_heartbeat);

        part_sn2->remote_vars_part_pa = remote_vars->vars_part_pa;
        dev_dbg(xpc_part, "  remote_vars_part_pa = 0x%016lx\n",
                part_sn2->remote_vars_part_pa);

        part_sn2->activate_IRQ_nasid = remote_vars->activate_IRQ_nasid;
        dev_dbg(xpc_part, "  activate_IRQ_nasid = 0x%x\n",
                part_sn2->activate_IRQ_nasid);

        part_sn2->activate_IRQ_phys_cpuid =
            remote_vars->activate_IRQ_phys_cpuid;
        dev_dbg(xpc_part, "  activate_IRQ_phys_cpuid = 0x%x\n",
                part_sn2->activate_IRQ_phys_cpuid);

        part_sn2->remote_amos_page_pa = remote_vars->amos_page_pa;
        dev_dbg(xpc_part, "  remote_amos_page_pa = 0x%lx\n",
                part_sn2->remote_amos_page_pa);

        part_sn2->remote_vars_version = remote_vars->version;
        dev_dbg(xpc_part, "  remote_vars_version = 0x%x\n",
                part_sn2->remote_vars_version);
}

/*
 * Prior code has determined the nasid which generated a activate IRQ.
 * Inspect that nasid to determine if its partition needs to be activated
 * or deactivated.
 *
 * A partition is considered "awaiting activation" if our partition
 * flags indicate it is not active and it has a heartbeat.  A
 * partition is considered "awaiting deactivation" if our partition
 * flags indicate it is active but it has no heartbeat or it is not
 * sending its heartbeat to us.
 *
 * To determine the heartbeat, the remote nasid must have a properly
 * initialized reserved page.
 */
static void
xpc_identify_activate_IRQ_req_sn2(int nasid)
{
        struct xpc_rsvd_page *remote_rp;
        struct xpc_vars_sn2 *remote_vars;
        unsigned long remote_rp_pa;
        unsigned long remote_vars_pa;
        int remote_rp_version;
        int reactivate = 0;
        unsigned long remote_rp_ts_jiffies = 0;
        short partid;
        struct xpc_partition *part;
        struct xpc_partition_sn2 *part_sn2;
        enum xp_retval ret;

        /* pull over the reserved page structure */

        remote_rp = (struct xpc_rsvd_page *)xpc_remote_copy_buffer_sn2;

        ret = xpc_get_remote_rp(nasid, NULL, remote_rp, &remote_rp_pa);
        if (ret != xpSuccess) {
                dev_warn(xpc_part, "unable to get reserved page from nasid %d, "
                         "which sent interrupt, reason=%d\n", nasid, ret);
                return;
        }

        remote_vars_pa = remote_rp->sn.sn2.vars_pa;
        remote_rp_version = remote_rp->version;
        remote_rp_ts_jiffies = remote_rp->ts_jiffies;

        partid = remote_rp->SAL_partid;
        part = &xpc_partitions[partid];
        part_sn2 = &part->sn.sn2;

        /* pull over the cross partition variables */

        remote_vars = (struct xpc_vars_sn2 *)xpc_remote_copy_buffer_sn2;

        ret = xpc_get_remote_vars_sn2(remote_vars_pa, remote_vars);
        if (ret != xpSuccess) {
                dev_warn(xpc_part, "unable to get XPC variables from nasid %d, "
                         "which sent interrupt, reason=%d\n", nasid, ret);

                XPC_DEACTIVATE_PARTITION(part, ret);
                return;
        }

        part->activate_IRQ_rcvd++;

        dev_dbg(xpc_part, "partid for nasid %d is %d; IRQs = %d; HB = "
                "%ld:0x%lx\n", (int)nasid, (int)partid, part->activate_IRQ_rcvd,
                remote_vars->heartbeat, remote_vars->heartbeating_to_mask[0]);

        if (xpc_partition_disengaged(part) &&
            part->act_state == XPC_P_AS_INACTIVE) {

                xpc_update_partition_info_sn2(part, remote_rp_version,
                                              &remote_rp_ts_jiffies,
                                              remote_rp_pa, remote_vars_pa,
                                              remote_vars);

                if (xpc_partition_deactivation_requested_sn2(partid)) {
                        /*
                         * Other side is waiting on us to deactivate even though
                         * we already have.
                         */
                        return;
                }

                xpc_activate_partition(part);
                return;
        }

        DBUG_ON(part->remote_rp_version == 0);
        DBUG_ON(part_sn2->remote_vars_version == 0);

        if (remote_rp_ts_jiffies != part->remote_rp_ts_jiffies) {

                /* the other side rebooted */

                DBUG_ON(xpc_partition_engaged_sn2(partid));
                DBUG_ON(xpc_partition_deactivation_requested_sn2(partid));

                xpc_update_partition_info_sn2(part, remote_rp_version,
                                              &remote_rp_ts_jiffies,
                                              remote_rp_pa, remote_vars_pa,
                                              remote_vars);
                reactivate = 1;
        }

        if (part->disengage_timeout > 0 && !xpc_partition_disengaged(part)) {
                /* still waiting on other side to disengage from us */
                return;
        }

        if (reactivate)
                XPC_DEACTIVATE_PARTITION(part, xpReactivating);
        else if (xpc_partition_deactivation_requested_sn2(partid))
                XPC_DEACTIVATE_PARTITION(part, xpOtherGoingDown);
}

/*
 * Loop through the activation amo variables and process any bits
 * which are set.  Each bit indicates a nasid sending a partition
 * activation or deactivation request.
 *
 * Return #of IRQs detected.
 */
int
xpc_identify_activate_IRQ_sender_sn2(void)
{
        int l;
        int b;
        unsigned long nasid_mask_long;
        u64 nasid;              /* remote nasid */
        int n_IRQs_detected = 0;
        struct amo *act_amos;

        act_amos = xpc_vars_sn2->amos_page + XPC_ACTIVATE_IRQ_AMOS_SN2;

        /* scan through activate amo variables looking for non-zero entries */
        for (l = 0; l < xpc_nasid_mask_nlongs; l++) {

                if (xpc_exiting)
                        break;

                nasid_mask_long = xpc_receive_IRQ_amo_sn2(&act_amos[l]);

                b = find_first_bit(&nasid_mask_long, BITS_PER_LONG);
                if (b >= BITS_PER_LONG) {
                        /* no IRQs from nasids in this amo variable */
                        continue;
                }

                dev_dbg(xpc_part, "amo[%d] gave back 0x%lx\n", l,
                        nasid_mask_long);

                /*
                 * If this nasid has been added to the machine since
                 * our partition was reset, this will retain the
                 * remote nasid in our reserved pages machine mask.
                 * This is used in the event of module reload.
                 */
                xpc_mach_nasids[l] |= nasid_mask_long;

                /* locate the nasid(s) which sent interrupts */

                do {
                        n_IRQs_detected++;
                        nasid = (l * BITS_PER_LONG + b) * 2;
                        dev_dbg(xpc_part, "interrupt from nasid %ld\n", nasid);
                        xpc_identify_activate_IRQ_req_sn2(nasid);

                        b = find_next_bit(&nasid_mask_long, BITS_PER_LONG,
                                          b + 1);
                } while (b < BITS_PER_LONG);
        }
        return n_IRQs_detected;
}

static void
xpc_process_activate_IRQ_rcvd_sn2(void)
{
        unsigned long irq_flags;
        int n_IRQs_expected;
        int n_IRQs_detected;

        spin_lock_irqsave(&xpc_activate_IRQ_rcvd_lock, irq_flags);
        n_IRQs_expected = xpc_activate_IRQ_rcvd;
        xpc_activate_IRQ_rcvd = 0;
        spin_unlock_irqrestore(&xpc_activate_IRQ_rcvd_lock, irq_flags);

        n_IRQs_detected = xpc_identify_activate_IRQ_sender_sn2();
        if (n_IRQs_detected < n_IRQs_expected) {
                /* retry once to help avoid missing amo */
                (void)xpc_identify_activate_IRQ_sender_sn2();
        }
}

/*
 * Setup the channel structures that are sn2 specific.
 */
static enum xp_retval
xpc_setup_ch_structures_sn_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        struct xpc_channel_sn2 *ch_sn2;
        enum xp_retval retval;
        int ret;
        int cpuid;
        int ch_number;
        struct timer_list *timer;
        short partid = XPC_PARTID(part);

        /* allocate all the required GET/PUT values */

        part_sn2->local_GPs =
            xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE, GFP_KERNEL,
                                          &part_sn2->local_GPs_base);
        if (part_sn2->local_GPs == NULL) {
                dev_err(xpc_chan, "can't get memory for local get/put "
                        "values\n");
                return xpNoMemory;
        }

        part_sn2->remote_GPs =
            xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE, GFP_KERNEL,
                                          &part_sn2->remote_GPs_base);
        if (part_sn2->remote_GPs == NULL) {
                dev_err(xpc_chan, "can't get memory for remote get/put "
                        "values\n");
                retval = xpNoMemory;
                goto out_1;
        }

        part_sn2->remote_GPs_pa = 0;

        /* allocate all the required open and close args */

        part_sn2->local_openclose_args =
            xpc_kzalloc_cacheline_aligned(XPC_OPENCLOSE_ARGS_SIZE,
                                          GFP_KERNEL, &part_sn2->
                                          local_openclose_args_base);
        if (part_sn2->local_openclose_args == NULL) {
                dev_err(xpc_chan, "can't get memory for local connect args\n");
                retval = xpNoMemory;
                goto out_2;
        }

        part_sn2->remote_openclose_args_pa = 0;

        part_sn2->local_chctl_amo_va = xpc_init_IRQ_amo_sn2(partid);

        part_sn2->notify_IRQ_nasid = 0;
        part_sn2->notify_IRQ_phys_cpuid = 0;
        part_sn2->remote_chctl_amo_va = NULL;

        sprintf(part_sn2->notify_IRQ_owner, "xpc%02d", partid);
        ret = request_irq(SGI_XPC_NOTIFY, xpc_handle_notify_IRQ_sn2,
                          IRQF_SHARED, part_sn2->notify_IRQ_owner,
                          (void *)(u64)partid);
        if (ret != 0) {
                dev_err(xpc_chan, "can't register NOTIFY IRQ handler, "
                        "errno=%d\n", -ret);
                retval = xpLackOfResources;
                goto out_3;
        }

        /* Setup a timer to check for dropped notify IRQs */
        timer = &part_sn2->dropped_notify_IRQ_timer;
        init_timer(timer);
        timer->function =
            (void (*)(unsigned long))xpc_check_for_dropped_notify_IRQ_sn2;
        timer->data = (unsigned long)part;
        timer->expires = jiffies + XPC_DROPPED_NOTIFY_IRQ_WAIT_INTERVAL;
        add_timer(timer);

        for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
                ch_sn2 = &part->channels[ch_number].sn.sn2;

                ch_sn2->local_GP = &part_sn2->local_GPs[ch_number];
                ch_sn2->local_openclose_args =
                    &part_sn2->local_openclose_args[ch_number];

                mutex_init(&ch_sn2->msg_to_pull_mutex);
        }

        /*
         * Setup the per partition specific variables required by the
         * remote partition to establish channel connections with us.
         *
         * The setting of the magic # indicates that these per partition
         * specific variables are ready to be used.
         */
        xpc_vars_part_sn2[partid].GPs_pa = xp_pa(part_sn2->local_GPs);
        xpc_vars_part_sn2[partid].openclose_args_pa =
            xp_pa(part_sn2->local_openclose_args);
        xpc_vars_part_sn2[partid].chctl_amo_pa =
            xp_pa(part_sn2->local_chctl_amo_va);
        cpuid = raw_smp_processor_id(); /* any CPU in this partition will do */
        xpc_vars_part_sn2[partid].notify_IRQ_nasid = cpuid_to_nasid(cpuid);
        xpc_vars_part_sn2[partid].notify_IRQ_phys_cpuid =
            cpu_physical_id(cpuid);
        xpc_vars_part_sn2[partid].nchannels = part->nchannels;
        xpc_vars_part_sn2[partid].magic = XPC_VP_MAGIC1_SN2;

        return xpSuccess;

        /* setup of ch structures failed */
out_3:
        kfree(part_sn2->local_openclose_args_base);
        part_sn2->local_openclose_args = NULL;
out_2:
        kfree(part_sn2->remote_GPs_base);
        part_sn2->remote_GPs = NULL;
out_1:
        kfree(part_sn2->local_GPs_base);
        part_sn2->local_GPs = NULL;
        return retval;
}

/*
 * Teardown the channel structures that are sn2 specific.
 */
static void
xpc_teardown_ch_structures_sn_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        short partid = XPC_PARTID(part);

        /*
         * Indicate that the variables specific to the remote partition are no
         * longer available for its use.
         */
        xpc_vars_part_sn2[partid].magic = 0;

        /* in case we've still got outstanding timers registered... */
        del_timer_sync(&part_sn2->dropped_notify_IRQ_timer);
        free_irq(SGI_XPC_NOTIFY, (void *)(u64)partid);

        kfree(part_sn2->local_openclose_args_base);
        part_sn2->local_openclose_args = NULL;
        kfree(part_sn2->remote_GPs_base);
        part_sn2->remote_GPs = NULL;
        kfree(part_sn2->local_GPs_base);
        part_sn2->local_GPs = NULL;
        part_sn2->local_chctl_amo_va = NULL;
}

/*
 * Create a wrapper that hides the underlying mechanism for pulling a cacheline
 * (or multiple cachelines) from a remote partition.
 *
 * src_pa must be a cacheline aligned physical address on the remote partition.
 * dst must be a cacheline aligned virtual address on this partition.
 * cnt must be cacheline sized
 */
/* ??? Replace this function by call to xp_remote_memcpy() or bte_copy()? */
static enum xp_retval
xpc_pull_remote_cachelines_sn2(struct xpc_partition *part, void *dst,
                               const unsigned long src_pa, size_t cnt)
{
        enum xp_retval ret;

        DBUG_ON(src_pa != L1_CACHE_ALIGN(src_pa));
        DBUG_ON((unsigned long)dst != L1_CACHE_ALIGN((unsigned long)dst));
        DBUG_ON(cnt != L1_CACHE_ALIGN(cnt));

        if (part->act_state == XPC_P_AS_DEACTIVATING)
                return part->reason;

        ret = xp_remote_memcpy(xp_pa(dst), src_pa, cnt);
        if (ret != xpSuccess) {
                dev_dbg(xpc_chan, "xp_remote_memcpy() from partition %d failed,"
                        " ret=%d\n", XPC_PARTID(part), ret);
        }
        return ret;
}

/*
 * Pull the remote per partition specific variables from the specified
 * partition.
 */
static enum xp_retval
xpc_pull_remote_vars_part_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        u8 buffer[L1_CACHE_BYTES * 2];
        struct xpc_vars_part_sn2 *pulled_entry_cacheline =
            (struct xpc_vars_part_sn2 *)L1_CACHE_ALIGN((u64)buffer);
        struct xpc_vars_part_sn2 *pulled_entry;
        unsigned long remote_entry_cacheline_pa;
        unsigned long remote_entry_pa;
        short partid = XPC_PARTID(part);
        enum xp_retval ret;

        /* pull the cacheline that contains the variables we're interested in */

        DBUG_ON(part_sn2->remote_vars_part_pa !=
                L1_CACHE_ALIGN(part_sn2->remote_vars_part_pa));
        DBUG_ON(sizeof(struct xpc_vars_part_sn2) != L1_CACHE_BYTES / 2);

        remote_entry_pa = part_sn2->remote_vars_part_pa +
            sn_partition_id * sizeof(struct xpc_vars_part_sn2);

        remote_entry_cacheline_pa = (remote_entry_pa & ~(L1_CACHE_BYTES - 1));

        pulled_entry = (struct xpc_vars_part_sn2 *)((u64)pulled_entry_cacheline
                                                    + (remote_entry_pa &
                                                    (L1_CACHE_BYTES - 1)));

        ret = xpc_pull_remote_cachelines_sn2(part, pulled_entry_cacheline,
                                             remote_entry_cacheline_pa,
                                             L1_CACHE_BYTES);
        if (ret != xpSuccess) {
                dev_dbg(xpc_chan, "failed to pull XPC vars_part from "
                        "partition %d, ret=%d\n", partid, ret);
                return ret;
        }

        /* see if they've been set up yet */

        if (pulled_entry->magic != XPC_VP_MAGIC1_SN2 &&
            pulled_entry->magic != XPC_VP_MAGIC2_SN2) {

                if (pulled_entry->magic != 0) {
                        dev_dbg(xpc_chan, "partition %d's XPC vars_part for "
                                "partition %d has bad magic value (=0x%lx)\n",
                                partid, sn_partition_id, pulled_entry->magic);
                        return xpBadMagic;
                }

                /* they've not been initialized yet */
                return xpRetry;
        }

        if (xpc_vars_part_sn2[partid].magic == XPC_VP_MAGIC1_SN2) {

                /* validate the variables */

                if (pulled_entry->GPs_pa == 0 ||
                    pulled_entry->openclose_args_pa == 0 ||
                    pulled_entry->chctl_amo_pa == 0) {

                        dev_err(xpc_chan, "partition %d's XPC vars_part for "
                                "partition %d are not valid\n", partid,
                                sn_partition_id);
                        return xpInvalidAddress;
                }

                /* the variables we imported look to be valid */

                part_sn2->remote_GPs_pa = pulled_entry->GPs_pa;
                part_sn2->remote_openclose_args_pa =
                    pulled_entry->openclose_args_pa;
                part_sn2->remote_chctl_amo_va =
                    (struct amo *)__va(pulled_entry->chctl_amo_pa);
                part_sn2->notify_IRQ_nasid = pulled_entry->notify_IRQ_nasid;
                part_sn2->notify_IRQ_phys_cpuid =
                    pulled_entry->notify_IRQ_phys_cpuid;

                if (part->nchannels > pulled_entry->nchannels)
                        part->nchannels = pulled_entry->nchannels;

                /* let the other side know that we've pulled their variables */

                xpc_vars_part_sn2[partid].magic = XPC_VP_MAGIC2_SN2;
        }

        if (pulled_entry->magic == XPC_VP_MAGIC1_SN2)
                return xpRetry;

        return xpSuccess;
}

/*
 * Establish first contact with the remote partititon. This involves pulling
 * the XPC per partition variables from the remote partition and waiting for
 * the remote partition to pull ours.
 */
static enum xp_retval
xpc_make_first_contact_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        enum xp_retval ret;

        /*
         * Register the remote partition's amos with SAL so it can handle
         * and cleanup errors within that address range should the remote
         * partition go down. We don't unregister this range because it is
         * difficult to tell when outstanding writes to the remote partition
         * are finished and thus when it is safe to unregister. This should
         * not result in wasted space in the SAL xp_addr_region table because
         * we should get the same page for remote_amos_page_pa after module
         * reloads and system reboots.
         */
        if (sn_register_xp_addr_region(part_sn2->remote_amos_page_pa,
                                       PAGE_SIZE, 1) < 0) {
                dev_warn(xpc_part, "xpc_activating(%d) failed to register "
                         "xp_addr region\n", XPC_PARTID(part));

                ret = xpPhysAddrRegFailed;
                XPC_DEACTIVATE_PARTITION(part, ret);
                return ret;
        }

        /*
         * Send activate IRQ to get other side to activate if they've not
         * already begun to do so.
         */
        xpc_send_activate_IRQ_sn2(part_sn2->remote_amos_page_pa,
                                  cnodeid_to_nasid(0),
                                  part_sn2->activate_IRQ_nasid,
                                  part_sn2->activate_IRQ_phys_cpuid);

        while ((ret = xpc_pull_remote_vars_part_sn2(part)) != xpSuccess) {
                if (ret != xpRetry) {
                        XPC_DEACTIVATE_PARTITION(part, ret);
                        return ret;
                }

                dev_dbg(xpc_part, "waiting to make first contact with "
                        "partition %d\n", XPC_PARTID(part));

                /* wait a 1/4 of a second or so */
                (void)msleep_interruptible(250);

                if (part->act_state == XPC_P_AS_DEACTIVATING)
                        return part->reason;
        }

        return xpSuccess;
}

/*
 * Get the chctl flags and pull the openclose args and/or remote GPs as needed.
 */
static u64
xpc_get_chctl_all_flags_sn2(struct xpc_partition *part)
{
        struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
        unsigned long irq_flags;
        union xpc_channel_ctl_flags chctl;
        enum xp_retval ret;

        /*
         * See if there are any chctl flags to be handled.
         */

        spin_lock_irqsave(&part->chctl_lock, irq_flags);
        chctl = part->chctl;
        if (chctl.all_flags != 0)
                part->chctl.all_flags = 0;

        spin_unlock_irqrestore(&part->chctl_lock, irq_flags);

        if (xpc_any_openclose_chctl_flags_set(&chctl)) {
                ret = xpc_pull_remote_cachelines_sn2(part, part->
                                                     remote_openclose_args,
                                                     part_sn2->
                                                     remote_openclose_args_pa,
                                                     XPC_OPENCLOSE_ARGS_SIZE);
                if (ret != xpSuccess) {
                        XPC_DEACTIVATE_PARTITION(part, ret);

                        dev_dbg(xpc_chan, "failed to pull openclose args from "
                                "partition %d, ret=%d\n", XPC_PARTID(part),
                                ret);

                        /* don't bother processing chctl flags anymore */
                        chctl.all_flags = 0;
                }
        }

        if (xpc_any_msg_chctl_flags_set(&chctl)) {
                ret = xpc_pull_remote_cachelines_sn2(part, part_sn2->remote_GPs,
                                                     part_sn2->remote_GPs_pa,
                                                     XPC_GP_SIZE);
                if (ret != xpSuccess) {
                        XPC_DEACTIVATE_PARTITION(part, ret);

                        dev_dbg(xpc_chan, "failed to pull GPs from partition "
                                "%d, ret=%d\n", XPC_PARTID(part), ret);

                        /* don't bother processing chctl flags anymore */
                        chctl.all_flags = 0;
                }
        }

        return chctl.all_flags;
}

/*
 * Allocate the local message queue and the notify queue.
 */
static enum xp_retval
xpc_allocate_local_msgqueue_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        unsigned long irq_flags;
        int nentries;
        size_t nbytes;

        for (nentries = ch->local_nentries; nentries > 0; nentries--) {

                nbytes = nentries * ch->entry_size;
                ch_sn2->local_msgqueue =
                    xpc_kzalloc_cacheline_aligned(nbytes, GFP_KERNEL,
                                                  &ch_sn2->local_msgqueue_base);
                if (ch_sn2->local_msgqueue == NULL)
                        continue;

                nbytes = nentries * sizeof(struct xpc_notify_sn2);
                ch_sn2->notify_queue = kzalloc(nbytes, GFP_KERNEL);
                if (ch_sn2->notify_queue == NULL) {
                        kfree(ch_sn2->local_msgqueue_base);
                        ch_sn2->local_msgqueue = NULL;
                        continue;
                }

                spin_lock_irqsave(&ch->lock, irq_flags);
                if (nentries < ch->local_nentries) {
                        dev_dbg(xpc_chan, "nentries=%d local_nentries=%d, "
                                "partid=%d, channel=%d\n", nentries,
                                ch->local_nentries, ch->partid, ch->number);

                        ch->local_nentries = nentries;
                }
                spin_unlock_irqrestore(&ch->lock, irq_flags);
                return xpSuccess;
        }

        dev_dbg(xpc_chan, "can't get memory for local message queue and notify "
                "queue, partid=%d, channel=%d\n", ch->partid, ch->number);
        return xpNoMemory;
}

/*
 * Allocate the cached remote message queue.
 */
static enum xp_retval
xpc_allocate_remote_msgqueue_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        unsigned long irq_flags;
        int nentries;
        size_t nbytes;

        DBUG_ON(ch->remote_nentries <= 0);

        for (nentries = ch->remote_nentries; nentries > 0; nentries--) {

                nbytes = nentries * ch->entry_size;
                ch_sn2->remote_msgqueue =
                    xpc_kzalloc_cacheline_aligned(nbytes, GFP_KERNEL, &ch_sn2->
                                                  remote_msgqueue_base);
                if (ch_sn2->remote_msgqueue == NULL)
                        continue;

                spin_lock_irqsave(&ch->lock, irq_flags);
                if (nentries < ch->remote_nentries) {
                        dev_dbg(xpc_chan, "nentries=%d remote_nentries=%d, "
                                "partid=%d, channel=%d\n", nentries,
                                ch->remote_nentries, ch->partid, ch->number);

                        ch->remote_nentries = nentries;
                }
                spin_unlock_irqrestore(&ch->lock, irq_flags);
                return xpSuccess;
        }

        dev_dbg(xpc_chan, "can't get memory for cached remote message queue, "
                "partid=%d, channel=%d\n", ch->partid, ch->number);
        return xpNoMemory;
}

/*
 * Allocate message queues and other stuff associated with a channel.
 *
 * Note: Assumes all of the channel sizes are filled in.
 */
static enum xp_retval
xpc_setup_msg_structures_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        enum xp_retval ret;

        DBUG_ON(ch->flags & XPC_C_SETUP);

        ret = xpc_allocate_local_msgqueue_sn2(ch);
        if (ret == xpSuccess) {

                ret = xpc_allocate_remote_msgqueue_sn2(ch);
                if (ret != xpSuccess) {
                        kfree(ch_sn2->local_msgqueue_base);
                        ch_sn2->local_msgqueue = NULL;
                        kfree(ch_sn2->notify_queue);
                        ch_sn2->notify_queue = NULL;
                }
        }
        return ret;
}

/*
 * Free up message queues and other stuff that were allocated for the specified
 * channel.
 */
static void
xpc_teardown_msg_structures_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;

        DBUG_ON(!spin_is_locked(&ch->lock));

        ch_sn2->remote_msgqueue_pa = 0;

        ch_sn2->local_GP->get = 0;
        ch_sn2->local_GP->put = 0;
        ch_sn2->remote_GP.get = 0;
        ch_sn2->remote_GP.put = 0;
        ch_sn2->w_local_GP.get = 0;
        ch_sn2->w_local_GP.put = 0;
        ch_sn2->w_remote_GP.get = 0;
        ch_sn2->w_remote_GP.put = 0;
        ch_sn2->next_msg_to_pull = 0;

        if (ch->flags & XPC_C_SETUP) {
                dev_dbg(xpc_chan, "ch->flags=0x%x, partid=%d, channel=%d\n",
                        ch->flags, ch->partid, ch->number);

                kfree(ch_sn2->local_msgqueue_base);
                ch_sn2->local_msgqueue = NULL;
                kfree(ch_sn2->remote_msgqueue_base);
                ch_sn2->remote_msgqueue = NULL;
                kfree(ch_sn2->notify_queue);
                ch_sn2->notify_queue = NULL;
        }
}

/*
 * Notify those who wanted to be notified upon delivery of their message.
 */
static void
xpc_notify_senders_sn2(struct xpc_channel *ch, enum xp_retval reason, s64 put)
{
        struct xpc_notify_sn2 *notify;
        u8 notify_type;
        s64 get = ch->sn.sn2.w_remote_GP.get - 1;

        while (++get < put && atomic_read(&ch->n_to_notify) > 0) {

                notify = &ch->sn.sn2.notify_queue[get % ch->local_nentries];

                /*
                 * See if the notify entry indicates it was associated with
                 * a message who's sender wants to be notified. It is possible
                 * that it is, but someone else is doing or has done the
                 * notification.
                 */
                notify_type = notify->type;
                if (notify_type == 0 ||
                    cmpxchg(&notify->type, notify_type, 0) != notify_type) {
                        continue;
                }

                DBUG_ON(notify_type != XPC_N_CALL);

                atomic_dec(&ch->n_to_notify);

                if (notify->func != NULL) {
                        dev_dbg(xpc_chan, "notify->func() called, notify=0x%p "
                                "msg_number=%ld partid=%d channel=%d\n",
                                (void *)notify, get, ch->partid, ch->number);

                        notify->func(reason, ch->partid, ch->number,
                                     notify->key);

                        dev_dbg(xpc_chan, "notify->func() returned, notify=0x%p"
                                " msg_number=%ld partid=%d channel=%d\n",
                                (void *)notify, get, ch->partid, ch->number);
                }
        }
}

static void
xpc_notify_senders_of_disconnect_sn2(struct xpc_channel *ch)
{
        xpc_notify_senders_sn2(ch, ch->reason, ch->sn.sn2.w_local_GP.put);
}

/*
 * Clear some of the msg flags in the local message queue.
 */
static inline void
xpc_clear_local_msgqueue_flags_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg;
        s64 get;

        get = ch_sn2->w_remote_GP.get;
        do {
                msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->local_msgqueue +
                                             (get % ch->local_nentries) *
                                             ch->entry_size);
                DBUG_ON(!(msg->flags & XPC_M_SN2_READY));
                msg->flags = 0;
        } while (++get < ch_sn2->remote_GP.get);
}

/*
 * Clear some of the msg flags in the remote message queue.
 */
static inline void
xpc_clear_remote_msgqueue_flags_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg;
        s64 put, remote_nentries = ch->remote_nentries;

        /* flags are zeroed when the buffer is allocated */
        if (ch_sn2->remote_GP.put < remote_nentries)
                return;

        put = max(ch_sn2->w_remote_GP.put, remote_nentries);
        do {
                msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->remote_msgqueue +
                                             (put % remote_nentries) *
                                             ch->entry_size);
                DBUG_ON(!(msg->flags & XPC_M_SN2_READY));
                DBUG_ON(!(msg->flags & XPC_M_SN2_DONE));
                DBUG_ON(msg->number != put - remote_nentries);
                msg->flags = 0;
        } while (++put < ch_sn2->remote_GP.put);
}

static int
xpc_n_of_deliverable_payloads_sn2(struct xpc_channel *ch)
{
        return ch->sn.sn2.w_remote_GP.put - ch->sn.sn2.w_local_GP.get;
}

static void
xpc_process_msg_chctl_flags_sn2(struct xpc_partition *part, int ch_number)
{
        struct xpc_channel *ch = &part->channels[ch_number];
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        int npayloads_sent;

        ch_sn2->remote_GP = part->sn.sn2.remote_GPs[ch_number];

        /* See what, if anything, has changed for each connected channel */

        xpc_msgqueue_ref(ch);

        if (ch_sn2->w_remote_GP.get == ch_sn2->remote_GP.get &&
            ch_sn2->w_remote_GP.put == ch_sn2->remote_GP.put) {
                /* nothing changed since GPs were last pulled */
                xpc_msgqueue_deref(ch);
                return;
        }

        if (!(ch->flags & XPC_C_CONNECTED)) {
                xpc_msgqueue_deref(ch);
                return;
        }

        /*
         * First check to see if messages recently sent by us have been
         * received by the other side. (The remote GET value will have
         * changed since we last looked at it.)
         */

        if (ch_sn2->w_remote_GP.get != ch_sn2->remote_GP.get) {

                /*
                 * We need to notify any senders that want to be notified
                 * that their sent messages have been received by their
                 * intended recipients. We need to do this before updating
                 * w_remote_GP.get so that we don't allocate the same message
                 * queue entries prematurely (see xpc_allocate_msg()).
                 */
                if (atomic_read(&ch->n_to_notify) > 0) {
                        /*
                         * Notify senders that messages sent have been
                         * received and delivered by the other side.
                         */
                        xpc_notify_senders_sn2(ch, xpMsgDelivered,
                                               ch_sn2->remote_GP.get);
                }

                /*
                 * Clear msg->flags in previously sent messages, so that
                 * they're ready for xpc_allocate_msg().
                 */
                xpc_clear_local_msgqueue_flags_sn2(ch);

                ch_sn2->w_remote_GP.get = ch_sn2->remote_GP.get;

                dev_dbg(xpc_chan, "w_remote_GP.get changed to %ld, partid=%d, "
                        "channel=%d\n", ch_sn2->w_remote_GP.get, ch->partid,
                        ch->number);

                /*
                 * If anyone was waiting for message queue entries to become
                 * available, wake them up.
                 */
                if (atomic_read(&ch->n_on_msg_allocate_wq) > 0)
                        wake_up(&ch->msg_allocate_wq);
        }

        /*
         * Now check for newly sent messages by the other side. (The remote
         * PUT value will have changed since we last looked at it.)
         */

        if (ch_sn2->w_remote_GP.put != ch_sn2->remote_GP.put) {
                /*
                 * Clear msg->flags in previously received messages, so that
                 * they're ready for xpc_get_deliverable_payload_sn2().
                 */
                xpc_clear_remote_msgqueue_flags_sn2(ch);

                smp_wmb(); /* ensure flags have been cleared before bte_copy */
                ch_sn2->w_remote_GP.put = ch_sn2->remote_GP.put;

                dev_dbg(xpc_chan, "w_remote_GP.put changed to %ld, partid=%d, "
                        "channel=%d\n", ch_sn2->w_remote_GP.put, ch->partid,
                        ch->number);

                npayloads_sent = xpc_n_of_deliverable_payloads_sn2(ch);
                if (npayloads_sent > 0) {
                        dev_dbg(xpc_chan, "msgs waiting to be copied and "
                                "delivered=%d, partid=%d, channel=%d\n",
                                npayloads_sent, ch->partid, ch->number);

                        if (ch->flags & XPC_C_CONNECTEDCALLOUT_MADE)
                                xpc_activate_kthreads(ch, npayloads_sent);
                }
        }

        xpc_msgqueue_deref(ch);
}

static struct xpc_msg_sn2 *
xpc_pull_remote_msg_sn2(struct xpc_channel *ch, s64 get)
{
        struct xpc_partition *part = &xpc_partitions[ch->partid];
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        unsigned long remote_msg_pa;
        struct xpc_msg_sn2 *msg;
        u32 msg_index;
        u32 nmsgs;
        u64 msg_offset;
        enum xp_retval ret;

        if (mutex_lock_interruptible(&ch_sn2->msg_to_pull_mutex) != 0) {
                /* we were interrupted by a signal */
                return NULL;
        }

        while (get >= ch_sn2->next_msg_to_pull) {

                /* pull as many messages as are ready and able to be pulled */

                msg_index = ch_sn2->next_msg_to_pull % ch->remote_nentries;

                DBUG_ON(ch_sn2->next_msg_to_pull >= ch_sn2->w_remote_GP.put);
                nmsgs = ch_sn2->w_remote_GP.put - ch_sn2->next_msg_to_pull;
                if (msg_index + nmsgs > ch->remote_nentries) {
                        /* ignore the ones that wrap the msg queue for now */
                        nmsgs = ch->remote_nentries - msg_index;
                }

                msg_offset = msg_index * ch->entry_size;
                msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->remote_msgqueue +
                    msg_offset);
                remote_msg_pa = ch_sn2->remote_msgqueue_pa + msg_offset;

                ret = xpc_pull_remote_cachelines_sn2(part, msg, remote_msg_pa,
                                                     nmsgs * ch->entry_size);
                if (ret != xpSuccess) {

                        dev_dbg(xpc_chan, "failed to pull %d msgs starting with"
                                " msg %ld from partition %d, channel=%d, "
                                "ret=%d\n", nmsgs, ch_sn2->next_msg_to_pull,
                                ch->partid, ch->number, ret);

                        XPC_DEACTIVATE_PARTITION(part, ret);

                        mutex_unlock(&ch_sn2->msg_to_pull_mutex);
                        return NULL;
                }

                ch_sn2->next_msg_to_pull += nmsgs;
        }

        mutex_unlock(&ch_sn2->msg_to_pull_mutex);

        /* return the message we were looking for */
        msg_offset = (get % ch->remote_nentries) * ch->entry_size;
        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->remote_msgqueue + msg_offset);

        return msg;
}

/*
 * Get the next deliverable message's payload.
 */
static void *
xpc_get_deliverable_payload_sn2(struct xpc_channel *ch)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg;
        void *payload = NULL;
        s64 get;

        do {
                if (ch->flags & XPC_C_DISCONNECTING)
                        break;

                get = ch_sn2->w_local_GP.get;
                smp_rmb();      /* guarantee that .get loads before .put */
                if (get == ch_sn2->w_remote_GP.put)
                        break;

                /* There are messages waiting to be pulled and delivered.
                 * We need to try to secure one for ourselves. We'll do this
                 * by trying to increment w_local_GP.get and hope that no one
                 * else beats us to it. If they do, we'll we'll simply have
                 * to try again for the next one.
                 */

                if (cmpxchg(&ch_sn2->w_local_GP.get, get, get + 1) == get) {
                        /* we got the entry referenced by get */

                        dev_dbg(xpc_chan, "w_local_GP.get changed to %ld, "
                                "partid=%d, channel=%d\n", get + 1,
                                ch->partid, ch->number);

                        /* pull the message from the remote partition */

                        msg = xpc_pull_remote_msg_sn2(ch, get);

                        if (msg != NULL) {
                                DBUG_ON(msg->number != get);
                                DBUG_ON(msg->flags & XPC_M_SN2_DONE);
                                DBUG_ON(!(msg->flags & XPC_M_SN2_READY));

                                payload = &msg->payload;
                        }
                        break;
                }

        } while (1);

        return payload;
}

/*
 * Now we actually send the messages that are ready to be sent by advancing
 * the local message queue's Put value and then send a chctl msgrequest to the
 * recipient partition.
 */
static void
xpc_send_msgs_sn2(struct xpc_channel *ch, s64 initial_put)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg;
        s64 put = initial_put + 1;
        int send_msgrequest = 0;

        while (1) {

                while (1) {
                        if (put == ch_sn2->w_local_GP.put)
                                break;

                        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->
                                                     local_msgqueue + (put %
                                                     ch->local_nentries) *
                                                     ch->entry_size);

                        if (!(msg->flags & XPC_M_SN2_READY))
                                break;

                        put++;
                }

                if (put == initial_put) {
                        /* nothing's changed */
                        break;
                }

                if (cmpxchg_rel(&ch_sn2->local_GP->put, initial_put, put) !=
                    initial_put) {
                        /* someone else beat us to it */
                        DBUG_ON(ch_sn2->local_GP->put < initial_put);
                        break;
                }

                /* we just set the new value of local_GP->put */

                dev_dbg(xpc_chan, "local_GP->put changed to %ld, partid=%d, "
                        "channel=%d\n", put, ch->partid, ch->number);

                send_msgrequest = 1;

                /*
                 * We need to ensure that the message referenced by
                 * local_GP->put is not XPC_M_SN2_READY or that local_GP->put
                 * equals w_local_GP.put, so we'll go have a look.
                 */
                initial_put = put;
        }

        if (send_msgrequest)
                xpc_send_chctl_msgrequest_sn2(ch);
}

/*
 * Allocate an entry for a message from the message queue associated with the
 * specified channel.
 */
static enum xp_retval
xpc_allocate_msg_sn2(struct xpc_channel *ch, u32 flags,
                     struct xpc_msg_sn2 **address_of_msg)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg;
        enum xp_retval ret;
        s64 put;

        /*
         * Get the next available message entry from the local message queue.
         * If none are available, we'll make sure that we grab the latest
         * GP values.
         */
        ret = xpTimeout;

        while (1) {

                put = ch_sn2->w_local_GP.put;
                smp_rmb();      /* guarantee that .put loads before .get */
                if (put - ch_sn2->w_remote_GP.get < ch->local_nentries) {

                        /* There are available message entries. We need to try
                         * to secure one for ourselves. We'll do this by trying
                         * to increment w_local_GP.put as long as someone else
                         * doesn't beat us to it. If they do, we'll have to
                         * try again.
                         */
                        if (cmpxchg(&ch_sn2->w_local_GP.put, put, put + 1) ==
                            put) {
                                /* we got the entry referenced by put */
                                break;
                        }
                        continue;       /* try again */
                }

                /*
                 * There aren't any available msg entries at this time.
                 *
                 * In waiting for a message entry to become available,
                 * we set a timeout in case the other side is not sending
                 * completion interrupts. This lets us fake a notify IRQ
                 * that will cause the notify IRQ handler to fetch the latest
                 * GP values as if an interrupt was sent by the other side.
                 */
                if (ret == xpTimeout)
                        xpc_send_chctl_local_msgrequest_sn2(ch);

                if (flags & XPC_NOWAIT)
                        return xpNoWait;

                ret = xpc_allocate_msg_wait(ch);
                if (ret != xpInterrupted && ret != xpTimeout)
                        return ret;
        }

        /* get the message's address and initialize it */
        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->local_msgqueue +
                                     (put % ch->local_nentries) *
                                     ch->entry_size);

        DBUG_ON(msg->flags != 0);
        msg->number = put;

        dev_dbg(xpc_chan, "w_local_GP.put changed to %ld; msg=0x%p, "
                "msg_number=%ld, partid=%d, channel=%d\n", put + 1,
                (void *)msg, msg->number, ch->partid, ch->number);

        *address_of_msg = msg;
        return xpSuccess;
}

/*
 * Common code that does the actual sending of the message by advancing the
 * local message queue's Put value and sends a chctl msgrequest to the
 * partition the message is being sent to.
 */
static enum xp_retval
xpc_send_payload_sn2(struct xpc_channel *ch, u32 flags, void *payload,
                     u16 payload_size, u8 notify_type, xpc_notify_func func,
                     void *key)
{
        enum xp_retval ret = xpSuccess;
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg = msg;
        struct xpc_notify_sn2 *notify = notify;
        s64 msg_number;
        s64 put;

        DBUG_ON(notify_type == XPC_N_CALL && func == NULL);

        if (XPC_MSG_SIZE(payload_size) > ch->entry_size)
                return xpPayloadTooBig;

        xpc_msgqueue_ref(ch);

        if (ch->flags & XPC_C_DISCONNECTING) {
                ret = ch->reason;
                goto out_1;
        }
        if (!(ch->flags & XPC_C_CONNECTED)) {
                ret = xpNotConnected;
                goto out_1;
        }

        ret = xpc_allocate_msg_sn2(ch, flags, &msg);
        if (ret != xpSuccess)
                goto out_1;

        msg_number = msg->number;

        if (notify_type != 0) {
                /*
                 * Tell the remote side to send an ACK interrupt when the
                 * message has been delivered.
                 */
                msg->flags |= XPC_M_SN2_INTERRUPT;

                atomic_inc(&ch->n_to_notify);

                notify = &ch_sn2->notify_queue[msg_number % ch->local_nentries];
                notify->func = func;
                notify->key = key;
                notify->type = notify_type;

                /* ??? Is a mb() needed here? */

                if (ch->flags & XPC_C_DISCONNECTING) {
                        /*
                         * An error occurred between our last error check and
                         * this one. We will try to clear the type field from
                         * the notify entry. If we succeed then
                         * xpc_disconnect_channel() didn't already process
                         * the notify entry.
                         */
                        if (cmpxchg(&notify->type, notify_type, 0) ==
                            notify_type) {
                                atomic_dec(&ch->n_to_notify);
                                ret = ch->reason;
                        }
                        goto out_1;
                }
        }

        memcpy(&msg->payload, payload, payload_size);

        msg->flags |= XPC_M_SN2_READY;

        /*
         * The preceding store of msg->flags must occur before the following
         * load of local_GP->put.
         */
        smp_mb();

        /* see if the message is next in line to be sent, if so send it */

        put = ch_sn2->local_GP->put;
        if (put == msg_number)
                xpc_send_msgs_sn2(ch, put);

out_1:
        xpc_msgqueue_deref(ch);
        return ret;
}

/*
 * Now we actually acknowledge the messages that have been delivered and ack'd
 * by advancing the cached remote message queue's Get value and if requested
 * send a chctl msgrequest to the message sender's partition.
 *
 * If a message has XPC_M_SN2_INTERRUPT set, send an interrupt to the partition
 * that sent the message.
 */
static void
xpc_acknowledge_msgs_sn2(struct xpc_channel *ch, s64 initial_get, u8 msg_flags)
{
        struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
        struct xpc_msg_sn2 *msg;
        s64 get = initial_get + 1;
        int send_msgrequest = 0;

        while (1) {

                while (1) {
                        if (get == ch_sn2->w_local_GP.get)
                                break;

                        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->
                                                     remote_msgqueue + (get %
                                                     ch->remote_nentries) *
                                                     ch->entry_size);

                        if (!(msg->flags & XPC_M_SN2_DONE))
                                break;

                        msg_flags |= msg->flags;
                        get++;
                }

                if (get == initial_get) {
                        /* nothing's changed */
                        break;
                }

                if (cmpxchg_rel(&ch_sn2->local_GP->get, initial_get, get) !=
                    initial_get) {
                        /* someone else beat us to it */
                        DBUG_ON(ch_sn2->local_GP->get <= initial_get);
                        break;
                }

                /* we just set the new value of local_GP->get */

                dev_dbg(xpc_chan, "local_GP->get changed to %ld, partid=%d, "
                        "channel=%d\n", get, ch->partid, ch->number);

                send_msgrequest = (msg_flags & XPC_M_SN2_INTERRUPT);

                /*
                 * We need to ensure that the message referenced by
                 * local_GP->get is not XPC_M_SN2_DONE or that local_GP->get
                 * equals w_local_GP.get, so we'll go have a look.
                 */
                initial_get = get;
        }

        if (send_msgrequest)
                xpc_send_chctl_msgrequest_sn2(ch);
}

static void
xpc_received_payload_sn2(struct xpc_channel *ch, void *payload)
{
        struct xpc_msg_sn2 *msg;
        s64 msg_number;
        s64 get;

        msg = container_of(payload, struct xpc_msg_sn2, payload);
        msg_number = msg->number;

        dev_dbg(xpc_chan, "msg=0x%p, msg_number=%ld, partid=%d, channel=%d\n",
                (void *)msg, msg_number, ch->partid, ch->number);

        DBUG_ON((((u64)msg - (u64)ch->sn.sn2.remote_msgqueue) / ch->entry_size) !=
                msg_number % ch->remote_nentries);
        DBUG_ON(!(msg->flags & XPC_M_SN2_READY));
        DBUG_ON(msg->flags & XPC_M_SN2_DONE);

        msg->flags |= XPC_M_SN2_DONE;

        /*
         * The preceding store of msg->flags must occur before the following
         * load of local_GP->get.
         */
        smp_mb();

        /*
         * See if this message is next in line to be acknowledged as having
         * been delivered.
         */
        get = ch->sn.sn2.local_GP->get;
        if (get == msg_number)
                xpc_acknowledge_msgs_sn2(ch, get, msg->flags);
}

int
xpc_init_sn2(void)
{
        int ret;
        size_t buf_size;

        xpc_setup_partitions_sn = xpc_setup_partitions_sn_sn2;
        xpc_teardown_partitions_sn = xpc_teardown_partitions_sn_sn2;
        xpc_get_partition_rsvd_page_pa = xpc_get_partition_rsvd_page_pa_sn2;
        xpc_setup_rsvd_page_sn = xpc_setup_rsvd_page_sn_sn2;

        xpc_allow_hb = xpc_allow_hb_sn2;
        xpc_disallow_hb = xpc_disallow_hb_sn2;
        xpc_disallow_all_hbs = xpc_disallow_all_hbs_sn2;
        xpc_increment_heartbeat = xpc_increment_heartbeat_sn2;
        xpc_offline_heartbeat = xpc_offline_heartbeat_sn2;
        xpc_online_heartbeat = xpc_online_heartbeat_sn2;
        xpc_heartbeat_init = xpc_heartbeat_init_sn2;
        xpc_heartbeat_exit = xpc_heartbeat_exit_sn2;
        xpc_get_remote_heartbeat = xpc_get_remote_heartbeat_sn2;

        xpc_request_partition_activation = xpc_request_partition_activation_sn2;
        xpc_request_partition_reactivation =
            xpc_request_partition_reactivation_sn2;
        xpc_request_partition_deactivation =
            xpc_request_partition_deactivation_sn2;
        xpc_cancel_partition_deactivation_request =
            xpc_cancel_partition_deactivation_request_sn2;

        xpc_process_activate_IRQ_rcvd = xpc_process_activate_IRQ_rcvd_sn2;
        xpc_setup_ch_structures_sn = xpc_setup_ch_structures_sn_sn2;
        xpc_teardown_ch_structures_sn = xpc_teardown_ch_structures_sn_sn2;
        xpc_make_first_contact = xpc_make_first_contact_sn2;

        xpc_get_chctl_all_flags = xpc_get_chctl_all_flags_sn2;
        xpc_send_chctl_closerequest = xpc_send_chctl_closerequest_sn2;
        xpc_send_chctl_closereply = xpc_send_chctl_closereply_sn2;
        xpc_send_chctl_openrequest = xpc_send_chctl_openrequest_sn2;
        xpc_send_chctl_openreply = xpc_send_chctl_openreply_sn2;

        xpc_save_remote_msgqueue_pa = xpc_save_remote_msgqueue_pa_sn2;

        xpc_setup_msg_structures = xpc_setup_msg_structures_sn2;
        xpc_teardown_msg_structures = xpc_teardown_msg_structures_sn2;

        xpc_notify_senders_of_disconnect = xpc_notify_senders_of_disconnect_sn2;
        xpc_process_msg_chctl_flags = xpc_process_msg_chctl_flags_sn2;
        xpc_n_of_deliverable_payloads = xpc_n_of_deliverable_payloads_sn2;
        xpc_get_deliverable_payload = xpc_get_deliverable_payload_sn2;

        xpc_indicate_partition_engaged = xpc_indicate_partition_engaged_sn2;
        xpc_indicate_partition_disengaged =
            xpc_indicate_partition_disengaged_sn2;
        xpc_partition_engaged = xpc_partition_engaged_sn2;
        xpc_any_partition_engaged = xpc_any_partition_engaged_sn2;
        xpc_assume_partition_disengaged = xpc_assume_partition_disengaged_sn2;

        xpc_send_payload = xpc_send_payload_sn2;
        xpc_received_payload = xpc_received_payload_sn2;

        if (offsetof(struct xpc_msg_sn2, payload) > XPC_MSG_HDR_MAX_SIZE) {
                dev_err(xpc_part, "header portion of struct xpc_msg_sn2 is "
                        "larger than %d\n", XPC_MSG_HDR_MAX_SIZE);
                return -E2BIG;
        }

        buf_size = max(XPC_RP_VARS_SIZE,
                       XPC_RP_HEADER_SIZE + XP_NASID_MASK_BYTES_SN2);
        xpc_remote_copy_buffer_sn2 = xpc_kmalloc_cacheline_aligned(buf_size,
                                                                   GFP_KERNEL,
                                              &xpc_remote_copy_buffer_base_sn2);
        if (xpc_remote_copy_buffer_sn2 == NULL) {
                dev_err(xpc_part, "can't get memory for remote copy buffer\n");
                return -ENOMEM;
        }

        /* open up protections for IPI and [potentially] amo operations */
        xpc_allow_IPI_ops_sn2();
        xpc_allow_amo_ops_shub_wars_1_1_sn2();

        /*
         * This is safe to do before the xpc_hb_checker thread has started
         * because the handler releases a wait queue.  If an interrupt is
         * received before the thread is waiting, it will not go to sleep,
         * but rather immediately process the interrupt.
         */
        ret = request_irq(SGI_XPC_ACTIVATE, xpc_handle_activate_IRQ_sn2, 0,
                          "xpc hb", NULL);
        if (ret != 0) {
                dev_err(xpc_part, "can't register ACTIVATE IRQ handler, "
                        "errno=%d\n", -ret);
                xpc_disallow_IPI_ops_sn2();
                kfree(xpc_remote_copy_buffer_base_sn2);
        }
        return ret;
}

void
xpc_exit_sn2(void)
{
        free_irq(SGI_XPC_ACTIVATE, NULL);
        xpc_disallow_IPI_ops_sn2();
        kfree(xpc_remote_copy_buffer_base_sn2);
}