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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2008-04-04 14:56:44 -0300 |
|---|---|---|
| committer | Avi Kivity <avi@qumranet.com> | 2008-04-27 12:00:58 +0300 |
| commit | bed1d1dfc4a458d82bcd258082638cbba860190d (patch) | |
| tree | 344f9cbf54082161e54ba77164f55aec695b9403 /arch/x86 | |
| parent | fcd6dbac9267c1c06a205ad8bb4bd027c0ace7f7 (diff) | |
| download | op-kernel-dev-bed1d1dfc4a458d82bcd258082638cbba860190d.zip op-kernel-dev-bed1d1dfc4a458d82bcd258082638cbba860190d.tar.gz | |
KVM: MMU: prepopulate guest pages after write-protecting
Zdenek reported a bug where a looping "dmsetup status" eventually hangs
on SMP guests.
The problem is that kvm_mmu_get_page() prepopulates the shadow MMU
before write protecting the guest page tables. By doing so, it leaves a
window open where the guest can mark a pte as present while the host has
shadow cached such pte as "notrap". Accesses to such address will fault
in the guest without the host having a chance to fix the situation.
Fix by moving the write protection before the pte prefetch.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/mmu.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 5c4c166..c89bf23 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -852,9 +852,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, sp->gfn = gfn; sp->role = role; hlist_add_head(&sp->hash_link, bucket); - vcpu->arch.mmu.prefetch_page(vcpu, sp); if (!metaphysical) rmap_write_protect(vcpu->kvm, gfn); + vcpu->arch.mmu.prefetch_page(vcpu, sp); return sp; } |
