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KVM: MMU: flush TLBs on writable -> read-only spte overwrite

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This can happen in the following scenario:

vcpu0			vcpu1
read fault
gup(.write=0)
			gup(.write=1)
			reuse swap cache, no COW
			set writable spte
			use writable spte
set read-only spte

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Marcelo Tosatti 2010-10-22 14:18:17 -02:00 committed by Avi Kivity
parent 982c25658c
commit 7905d9a5ad
1 changed files with 10 additions and 0 deletions
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10
arch/x86/kvm/mmu.c
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@ -2069,6 +2069,16 @@ 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;
}