From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Fri, 4 Apr 2008 17:56:44 +0000 (-0300)
Subject: KVM: MMU: prepopulate guest pages after write-protecting
X-Git-Tag: v2.6.26-rc1~1028^2~50
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bed1d1dfc4a458d82bcd258082638cbba860190d;p=pandora-kernel.git

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>
---

Reading git-diff-tree failed