KVM: MMU: fast prefetch spte on invlpg path

Fast prefetch spte for the unsync shadow page on invlpg path

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

4 files changed, 36 insertions, 40 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f8ab0d760231..3c9ea26c7aea 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -461,7 +461,6 @@ struct kvm_arch {
         unsigned int n_requested_mmu_pages;
         unsigned int n_max_mmu_pages;
         unsigned int indirect_shadow_pages;
-        atomic_t invlpg_counter;
         struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
         /*
          * Hash table of struct kvm_mmu_page.
@@ -757,8 +756,7 @@ int fx_init(struct kvm_vcpu *vcpu);
 
 void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu);
 void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
-                       const u8 *new, int bytes,
-                       bool guest_initiated);
+                       const u8 *new, int bytes);
 int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
 int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
 void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index d15f908649e7..c01137f10c6b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3531,8 +3531,7 @@ static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
 }
 
 void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
-                       const u8 *new, int bytes,
-                       bool guest_initiated)
+                       const u8 *new, int bytes)
 {
         gfn_t gfn = gpa >> PAGE_SHIFT;
         union kvm_mmu_page_role mask = { .word = 0 };
@@ -3541,7 +3540,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
         LIST_HEAD(invalid_list);
         u64 entry, gentry, *spte;
         unsigned pte_size, page_offset, misaligned, quadrant, offset;
-        int level, npte, invlpg_counter, r, flooded = 0;
+        int level, npte, r, flooded = 0;
         bool remote_flush, local_flush, zap_page;
 
         /*
@@ -3556,19 +3555,16 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 
         pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
 
-        invlpg_counter = atomic_read(&vcpu->kvm->arch.invlpg_counter);
-
         /*
          * Assume that the pte write on a page table of the same type
          * as the current vcpu paging mode since we update the sptes only
          * when they have the same mode.
          */
-        if ((is_pae(vcpu) && bytes == 4) || !new) {
+        if (is_pae(vcpu) && bytes == 4) {
                 /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
-                if (is_pae(vcpu)) {
-                        gpa &= ~(gpa_t)7;
-                        bytes = 8;
-                }
+                gpa &= ~(gpa_t)7;
+                bytes = 8;
+
                 r = kvm_read_guest(vcpu->kvm, gpa, &gentry, min(bytes, 8));
                 if (r)
                         gentry = 0;
@@ -3594,22 +3590,18 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
          */
         mmu_topup_memory_caches(vcpu);
         spin_lock(&vcpu->kvm->mmu_lock);
-        if (atomic_read(&vcpu->kvm->arch.invlpg_counter) != invlpg_counter)
-                gentry = 0;
         kvm_mmu_free_some_pages(vcpu);
         ++vcpu->kvm->stat.mmu_pte_write;
         trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);
-        if (guest_initiated) {
-                if (gfn == vcpu->arch.last_pt_write_gfn
-                    && !last_updated_pte_accessed(vcpu)) {
-                        ++vcpu->arch.last_pt_write_count;
-                        if (vcpu->arch.last_pt_write_count >= 3)
-                                flooded = 1;
-                } else {
-                        vcpu->arch.last_pt_write_gfn = gfn;
-                        vcpu->arch.last_pt_write_count = 1;
-                        vcpu->arch.last_pte_updated = NULL;
-                }
+        if (gfn == vcpu->arch.last_pt_write_gfn
+            && !last_updated_pte_accessed(vcpu)) {
+                ++vcpu->arch.last_pt_write_count;
+                if (vcpu->arch.last_pt_write_count >= 3)
+                        flooded = 1;
+        } else {
+                vcpu->arch.last_pt_write_gfn = gfn;
+                vcpu->arch.last_pt_write_count = 1;
+                vcpu->arch.last_pte_updated = NULL;
         }
 
         mask.cr0_wp = mask.cr4_pae = mask.nxe = 1;
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index d8d3906649da..9efb86035774 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -672,20 +672,27 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 {
         struct kvm_shadow_walk_iterator iterator;
         struct kvm_mmu_page *sp;
-        gpa_t pte_gpa = -1;
         int level;
         u64 *sptep;
 
         vcpu_clear_mmio_info(vcpu, gva);
 
-        spin_lock(&vcpu->kvm->mmu_lock);
+        /*
+         * No need to check return value here, rmap_can_add() can
+         * help us to skip pte prefetch later.
+         */
+        mmu_topup_memory_caches(vcpu);
 
+        spin_lock(&vcpu->kvm->mmu_lock);
         for_each_shadow_entry(vcpu, gva, iterator) {
                 level = iterator.level;
                 sptep = iterator.sptep;
 
                 sp = page_header(__pa(sptep));
                 if (is_last_spte(*sptep, level)) {
+                        pt_element_t gpte;
+                        gpa_t pte_gpa;
+
                         if (!sp->unsync)
                                 break;
 
@@ -694,22 +701,21 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
 
                         if (mmu_page_zap_pte(vcpu->kvm, sp, sptep))
                                 kvm_flush_remote_tlbs(vcpu->kvm);
+
+                        if (!rmap_can_add(vcpu))
+                                break;
+
+                        if (kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte,
+                                                  sizeof(pt_element_t)))
+                                break;
+
+                        FNAME(update_pte)(vcpu, sp, sptep, &gpte);
                 }
 
                 if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
                         break;
         }
-
-        atomic_inc(&vcpu->kvm->arch.invlpg_counter);
-
         spin_unlock(&vcpu->kvm->mmu_lock);
-
-        if (pte_gpa == -1)
-                return;
-
-        if (mmu_topup_memory_caches(vcpu))
-                return;
-        kvm_mmu_pte_write(vcpu, pte_gpa, NULL, sizeof(pt_element_t), 0);
 }
 
 static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a2154487917d..9c980ce26e61 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4087,7 +4087,7 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
         ret = kvm_write_guest(vcpu->kvm, gpa, val, bytes);
         if (ret < 0)
                 return 0;
-        kvm_mmu_pte_write(vcpu, gpa, val, bytes, 1);
+        kvm_mmu_pte_write(vcpu, gpa, val, bytes);
         return 1;
 }
 
@@ -4324,7 +4324,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
         if (!exchanged)
                 return X86EMUL_CMPXCHG_FAILED;
 
-        kvm_mmu_pte_write(vcpu, gpa, new, bytes, 1);
+        kvm_mmu_pte_write(vcpu, gpa, new, bytes);
 
         return X86EMUL_CONTINUE;