[PATCH v3 2/6] KVM: MMU: don't drop spte if overwrite it from W to RO

Xiao Guangrong
2010-11-19T08:58:21Z

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>
---
arch/x86/kvm/mmu.c | 20 +++++++++-----------
1 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index bdb9fa9..59b5bd2 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;
}
--
1.7.0.4