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authorMarcelo Tosatti <mtosatti@redhat.com>2008-04-04 14:56:44 -0300
committerAvi Kivity <avi@qumranet.com>2008-04-27 12:00:58 +0300
commitbed1d1dfc4a458d82bcd258082638cbba860190d (patch)
tree344f9cbf54082161e54ba77164f55aec695b9403 /arch/x86
parentfcd6dbac9267c1c06a205ad8bb4bd027c0ace7f7 (diff)
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.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5c4c16662c6..c89bf230af6 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;
}