tree 344f9cbf54082161e54ba77164f55aec695b9403
parent fcd6dbac9267c1c06a205ad8bb4bd027c0ace7f7
author Marcelo Tosatti <mtosatti@redhat.com> 1207331804 -0300
committer Avi Kivity <avi@qumranet.com> 1209286858 +0300

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>