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>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ab100a7..29b2ec4 100644 (file)
--- 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;
        }