KVM: MMU: fast invalidate all mmio sptes
This patch tries to introduce a very simple and scale way to invalidate
all mmio sptes - it need not walk any shadow pages and hold mmu-lock
KVM maintains a global mmio valid generation-number which is stored in
kvm->memslots.generation and every mmio spte stores the current global
generation-number into his available bits when it is created
When KVM need zap all mmio sptes, it just simply increase the global
generation-number. When guests do mmio access, KVM intercepts a MMIO #PF
then it walks the shadow page table and get the mmio spte. If the
generation-number on the spte does not equal the global generation-number,
it will go to the normal #PF handler to update the mmio spte
Since 19 bits are used to store generation-number on mmio spte, we zap all
mmio sptes when the number is round
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 476d155..3e893cd 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -205,9 +205,11 @@
#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)
{
@@ -231,17 +233,23 @@
return gen;
}
+static unsigned int kvm_current_mmio_generation(struct kvm *kvm)
+{
+ return kvm_memslots(kvm)->generation & 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);
}
@@ -273,6 +281,12 @@
return false;
}
+static bool check_mmio_spte(struct kvm *kvm, u64 spte)
+{
+ return likely(get_mmio_spte_generation(spte) ==
+ kvm_current_mmio_generation(kvm));
+}
+
static inline u64 rsvd_bits(int s, int e)
{
return ((1ULL << (e - s + 1)) - 1) << s;
@@ -3237,6 +3251,9 @@
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;
@@ -3278,8 +3295,12 @@
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)
@@ -3355,8 +3376,12 @@
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)
@@ -4329,7 +4354,7 @@
spin_unlock(&kvm->mmu_lock);
}
-void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
+static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
LIST_HEAD(invalid_list);
@@ -4352,6 +4377,19 @@
return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
}
+void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
+{
+ /*
+ * 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)))
+ kvm_mmu_zap_mmio_sptes(kvm);
+}
+
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
{
struct kvm *kvm;