KVM: MMU: optimize to handle dirty bit

If dirty bit is not set, we can make the pte access read-only to avoid handing
dirty bit everywhere

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

1 files changed, 6 insertions, 7 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index d1986b7dcec7..98812c25727b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1923,7 +1923,7 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
 
 static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                     unsigned pte_access, int user_fault,
-                    int write_fault, int dirty, int level,
+                    int write_fault, int level,
                     gfn_t gfn, pfn_t pfn, bool speculative,
                     bool can_unsync, bool host_writable)
 {
@@ -1938,8 +1938,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
         spte = PT_PRESENT_MASK;
         if (!speculative)
                 spte |= shadow_accessed_mask;
-        if (!dirty)
-                pte_access &= ~ACC_WRITE_MASK;
+
         if (pte_access & ACC_EXEC_MASK)
                 spte |= shadow_x_mask;
         else
@@ -2023,7 +2022,7 @@ done:
 
 static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                          unsigned pt_access, unsigned pte_access,
-                         int user_fault, int write_fault, int dirty,
+                         int user_fault, int write_fault,
                          int *ptwrite, int level, gfn_t gfn,
                          pfn_t pfn, bool speculative,
                          bool host_writable)
@@ -2059,7 +2058,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
         }
 
         if (set_spte(vcpu, sptep, pte_access, user_fault, write_fault,
-                      dirty, level, gfn, pfn, speculative, true,
+                      level, gfn, pfn, speculative, true,
                       host_writable)) {
                 if (write_fault)
                         *ptwrite = 1;
@@ -2129,7 +2128,7 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
 
         for (i = 0; i < ret; i++, gfn++, start++)
                 mmu_set_spte(vcpu, start, ACC_ALL,
-                             access, 0, 0, 1, NULL,
+                             access, 0, 0, NULL,
                              sp->role.level, gfn,
                              page_to_pfn(pages[i]), true, true);
 
@@ -2193,7 +2192,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
                         unsigned pte_access = ACC_ALL;
 
                         mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, pte_access,
-                                     0, write, 1, &pt_write,
+                                     0, write, &pt_write,
                                      level, gfn, pfn, prefault, map_writable);
                         direct_pte_prefetch(vcpu, iterator.sptep);
                         ++vcpu->stat.pf_fixed;