#define MMIO_SPTE_GEN_LOW_SHIFT 3
#define MMIO_SPTE_GEN_HIGH_SHIFT 52
+#define MMIO_GEN_SHIFT 19
#define MMIO_GEN_LOW_SHIFT 9
#define MMIO_GEN_LOW_MASK ((1 << MMIO_GEN_LOW_SHIFT) - 1)
-#define MMIO_MAX_GEN ((1 << 19) - 1)
+#define MMIO_GEN_MASK ((1 << MMIO_GEN_SHIFT) - 1)
+#define MMIO_MAX_GEN ((1 << MMIO_GEN_SHIFT) - 1)
static u64 generation_mmio_spte_mask(unsigned int gen)
{
return gen;
}
+static unsigned int kvm_current_mmio_generation(struct kvm *kvm)
+{
+ /*
+ * Init kvm generation close to MMIO_MAX_GEN to easily test the
+ * code of handling generation number wrap-around.
+ */
+ return (kvm_memslots(kvm)->generation +
+ MMIO_MAX_GEN - 150) & MMIO_GEN_MASK;
+}
+
static void mark_mmio_spte(struct kvm *kvm, u64 *sptep, u64 gfn,
unsigned access)
{
- struct kvm_mmu_page *sp = page_header(__pa(sptep));
- u64 mask = generation_mmio_spte_mask(0);
+ unsigned int gen = kvm_current_mmio_generation(kvm);
+ u64 mask = generation_mmio_spte_mask(gen);
access &= ACC_WRITE_MASK | ACC_USER_MASK;
mask |= shadow_mmio_mask | access | gfn << PAGE_SHIFT;
- sp->mmio_cached = true;
- trace_mark_mmio_spte(sptep, gfn, access, 0);
+ trace_mark_mmio_spte(sptep, gfn, access, gen);
mmu_spte_set(sptep, mask);
}
return false;
}
+static bool check_mmio_spte(struct kvm *kvm, u64 spte)
+{
+ unsigned int kvm_gen, spte_gen;
+
+ kvm_gen = kvm_current_mmio_generation(kvm);
+ spte_gen = get_mmio_spte_generation(spte);
+
+ trace_check_mmio_spte(spte, kvm_gen, spte_gen);
+ return likely(kvm_gen == spte_gen);
+}
+
static inline u64 rsvd_bits(int s, int e)
{
return ((1ULL << (e - s + 1)) - 1) << s;
/*
* The idea using the light way get the spte on x86_32 guest is from
* gup_get_pte(arch/x86/mm/gup.c).
- * The difference is we can not catch the spte tlb flush if we leave
- * guest mode, so we emulate it by increase clear_spte_count when spte
- * is cleared.
+ *
+ * An spte tlb flush may be pending, because kvm_set_pte_rmapp
+ * coalesces them and we are running out of the MMU lock. Therefore
+ * we need to protect against in-progress updates of the spte.
+ *
+ * Reading the spte while an update is in progress may get the old value
+ * for the high part of the spte. The race is fine for a present->non-present
+ * change (because the high part of the spte is ignored for non-present spte),
+ * but for a present->present change we must reread the spte.
+ *
+ * All such changes are done in two steps (present->non-present and
+ * non-present->present), hence it is enough to count the number of
+ * present->non-present updates: if it changed while reading the spte,
+ * we might have hit the race. This is done using clear_spte_count.
*/
static u64 __get_spte_lockless(u64 *sptep)
{
return spte;
}
-/*
- * If it is a real mmio page fault, return 1 and emulat the instruction
- * directly, return 0 to let CPU fault again on the address, -1 is
- * returned if bug is detected.
- */
int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
u64 spte;
if (quickly_check_mmio_pf(vcpu, addr, direct))
- return 1;
+ return RET_MMIO_PF_EMULATE;
spte = walk_shadow_page_get_mmio_spte(vcpu, addr);
gfn_t gfn = get_mmio_spte_gfn(spte);
unsigned access = get_mmio_spte_access(spte);
+ if (!check_mmio_spte(vcpu->kvm, spte))
+ return RET_MMIO_PF_INVALID;
+
if (direct)
addr = 0;
trace_handle_mmio_page_fault(addr, gfn, access);
vcpu_cache_mmio_info(vcpu, addr, gfn, access);
- return 1;
+ return RET_MMIO_PF_EMULATE;
}
/*
* it's a BUG if the gfn is not a mmio page.
*/
if (direct && !check_direct_spte_mmio_pf(spte))
- return -1;
+ return RET_MMIO_PF_BUG;
/*
* If the page table is zapped by other cpus, let CPU fault again on
* the address.
*/
- return 0;
+ return RET_MMIO_PF_RETRY;
}
EXPORT_SYMBOL_GPL(handle_mmio_page_fault_common);
int ret;
ret = handle_mmio_page_fault_common(vcpu, addr, direct);
- WARN_ON(ret < 0);
+ WARN_ON(ret == RET_MMIO_PF_BUG);
return ret;
}
pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code);
- if (unlikely(error_code & PFERR_RSVD_MASK))
- return handle_mmio_page_fault(vcpu, gva, error_code, true);
+ if (unlikely(error_code & PFERR_RSVD_MASK)) {
+ r = handle_mmio_page_fault(vcpu, gva, error_code, true);
+
+ if (likely(r != RET_MMIO_PF_INVALID))
+ return r;
+ }
r = mmu_topup_memory_caches(vcpu);
if (r)
ASSERT(vcpu);
ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));
- if (unlikely(error_code & PFERR_RSVD_MASK))
- return handle_mmio_page_fault(vcpu, gpa, error_code, true);
+ if (unlikely(error_code & PFERR_RSVD_MASK)) {
+ r = handle_mmio_page_fault(vcpu, gpa, error_code, true);
+
+ if (likely(r != RET_MMIO_PF_INVALID))
+ return r;
+ }
r = mmu_topup_memory_caches(vcpu);
if (r)
spin_unlock(&kvm->mmu_lock);
}
-void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
+static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
{
- struct kvm_mmu_page *sp, *node;
- LIST_HEAD(invalid_list);
-
- spin_lock(&kvm->mmu_lock);
-restart:
- list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
- if (!sp->mmio_cached)
- continue;
- if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
- goto restart;
- }
-
- kvm_mmu_commit_zap_page(kvm, &invalid_list);
- spin_unlock(&kvm->mmu_lock);
+ return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
}
-static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
+void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
{
- return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
+ /*
+ * The very rare case: if the generation-number is round,
+ * zap all shadow pages.
+ *
+ * The max value is MMIO_MAX_GEN - 1 since it is not called
+ * when mark memslot invalid.
+ */
+ if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1))) {
+ printk_ratelimited(KERN_INFO "kvm: zapping shadow pages for mmio generation wraparound\n");
+ kvm_mmu_invalidate_zap_all_pages(kvm);
+ }
}
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
projects / ~andy / linux / blobdiff