KVM: MMU: don't drop spte if overwrite it from W to RO

We just need flush tlb if overwrite a writable spte with a read-only one.

And we should move this operation to set_spte() for sync_page path

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

1 files changed, 9 insertions, 11 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ab100a7e0c49..29b2ec46bf1e 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1960,7 +1960,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                     gfn_t gfn, pfn_t pfn, bool speculative,
                     bool can_unsync, bool reset_host_protection)
 {
-        u64 spte;
+        u64 spte, entry = *sptep;
         int ret = 0;
 
         /*
@@ -2031,6 +2031,14 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 
 set_pte:
         update_spte(sptep, spte);
+        /*
+         * If we overwrite a writable spte with a read-only one we
+         * should flush remote TLBs. Otherwise rmap_write_protect
+         * will find a read-only spte, even though the writable spte
+         * might be cached on a CPU's TLB.
+         */
+        if (is_writable_pte(entry) && !is_writable_pte(*sptep))
+                kvm_flush_remote_tlbs(vcpu->kvm);
 done:
         return ret;
 }
@@ -2069,16 +2077,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                                  spte_to_pfn(*sptep), pfn);
                         drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);
                         kvm_flush_remote_tlbs(vcpu->kvm);
-                /*
-                 * If we overwrite a writable spte with a read-only one,
-                 * drop it and flush remote TLBs. Otherwise rmap_write_protect
-                 * will find a read-only spte, even though the writable spte
-                 * might be cached on a CPU's TLB.
-                 */
-                } else if (is_writable_pte(*sptep) &&
-                          (!(pte_access & ACC_WRITE_MASK) || !dirty)) {
-                        drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);
-                        kvm_flush_remote_tlbs(vcpu->kvm);
                 } else
                         was_rmapped = 1;
         }