KVM: MMU: combine guest pte read between fetch and pte prefetch

Combine guest pte read between guest pte check in the fetch path and pte prefetch

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 21 insertions, 19 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 872ff265c91e..a4e8389df2ad 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -67,6 +67,7 @@ struct guest_walker {
         int level;
         gfn_t table_gfn[PT_MAX_FULL_LEVELS];
         pt_element_t ptes[PT_MAX_FULL_LEVELS];
+        pt_element_t prefetch_ptes[PTE_PREFETCH_NUM];
         gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
         unsigned pt_access;
         unsigned pte_access;
@@ -302,21 +303,33 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 static bool FNAME(gpte_changed)(struct kvm_vcpu *vcpu,
                                 struct guest_walker *gw, int level)
 {
-        int r;
         pt_element_t curr_pte;
-
-        r = kvm_read_guest_atomic(vcpu->kvm, gw->pte_gpa[level - 1],
+        gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1];
+        u64 mask;
+        int r, index;
+
+        if (level == PT_PAGE_TABLE_LEVEL) {
+                mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1;
+                base_gpa = pte_gpa & ~mask;
+                index = (pte_gpa - base_gpa) / sizeof(pt_element_t);
+
+                r = kvm_read_guest_atomic(vcpu->kvm, base_gpa,
+                                gw->prefetch_ptes, sizeof(gw->prefetch_ptes));
+                curr_pte = gw->prefetch_ptes[index];
+        } else
+                r = kvm_read_guest_atomic(vcpu->kvm, pte_gpa,
                                   &curr_pte, sizeof(curr_pte));
+
         return r || curr_pte != gw->ptes[level - 1];
 }
 
-static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
+static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
+                                u64 *sptep)
 {
         struct kvm_mmu_page *sp;
-        pt_element_t gptep[PTE_PREFETCH_NUM];
-        gpa_t first_pte_gpa;
-        int offset = 0, i;
+        pt_element_t *gptep = gw->prefetch_ptes;
         u64 *spte;
+        int i;
 
         sp = page_header(__pa(sptep));
 
@@ -327,17 +340,6 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
                 return __direct_pte_prefetch(vcpu, sp, sptep);
 
         i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
-
-        if (PTTYPE == 32)
-                offset = sp->role.quadrant << PT64_LEVEL_BITS;
-
-        first_pte_gpa = gfn_to_gpa(sp->gfn) +
-                                (offset + i) * sizeof(pt_element_t);
-
-        if (kvm_read_guest_atomic(vcpu->kvm, first_pte_gpa, gptep,
-                                        sizeof(gptep)) < 0)
-                return;
-
         spte = sp->spt + i;
 
         for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
@@ -462,7 +464,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
         mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access,
                      user_fault, write_fault, dirty, ptwrite, it.level,
                      gw->gfn, pfn, false, true);
-        FNAME(pte_prefetch)(vcpu, it.sptep);
+        FNAME(pte_prefetch)(vcpu, gw, it.sptep);
 
         return it.sptep;