]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
KVM: MMU: prepopulate guest pages after write-protecting
authorMarcelo Tosatti <mtosatti@redhat.com>
Fri, 4 Apr 2008 17:56:44 +0000 (14:56 -0300)
committerAvi Kivity <avi@qumranet.com>
Sun, 27 Apr 2008 09:00:58 +0000 (12:00 +0300)
commitbed1d1dfc4a458d82bcd258082638cbba860190d
tree344f9cbf54082161e54ba77164f55aec695b9403
parentfcd6dbac9267c1c06a205ad8bb4bd027c0ace7f7
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>
arch/x86/kvm/mmu.c