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>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f8ab0d7..3c9ea26 100644 (file)
--- 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 d15f908..c01137f 100644 (file)
--- 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 d8d3906..9efb860 100644 (file)
--- 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 a215448..9c980ce 100644 (file)
--- 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;