From 18735b09c490c145bf9174e438a2408bfbd66b76 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@redhat.com>
Date: Sun, 18 Jul 2010 12:54:31 -0300
Subject: [PATCH] KVM: MMU: fix conflict access permissions in direct sp

RH-Author: Avi Kivity <avi@redhat.com>
Message-id: <1279457671-16095-1-git-send-email-avi@redhat.com>
Patchwork-id: 10778
O-Subject: [PATCH RHEL5.6 RHEL5.5.z] KVM: MMU: fix conflict access permissions
	in direct sp
Bugzilla: 615225
RH-Acked-by: Andrea Arcangeli <aarcange@redhat.com>
RH-Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>

From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>

 Bugzilla: 615225 (R6B crashes as a guest on R6B)
 Upstream: kvm.git 06f334e2b509b4c9f6c4cec7e0e56444a2730922

In no-direct mapping, we mark sp is 'direct' when we mapping the
guest's larger page, but its access is encoded form upper page-struct
entire not include the last mapping, it will cause access conflict.

For example, have this mapping:
        [W]
      / PDE1 -> |---|
  P[W]          |   | LPA
      \ PDE2 -> |---|
        [R]

P have two children, PDE1 and PDE2, both PDE1 and PDE2 mapping the
same lage page(LPA). The P's access is WR, PDE1's access is WR,
PDE2's access is RO(just consider read-write permissions here)

When guest access PDE1, we will create a direct sp for LPA, the sp's
access is from P, is W, then we will mark the ptes is W in this sp.

Then, guest access PDE2, we will find LPA's shadow page, is the same as
PDE's, and mark the ptes is RO.

So, if guest access PDE1, the incorrect #PF is occured.

Fixed by encode the last mapping access into direct shadow page

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
 arch/x86/kvm/paging_tmpl.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 arch/x86/kvm/paging_tmpl.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 3edb7c4..078dae4 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -326,6 +326,7 @@ static int FNAME(shadow_walk_entry)(struct kvm_shadow_walk *_sw,
 		if (!is_dirty_pte(gw->ptes[level - 1]))
 			access &= ~ACC_WRITE_MASK;
 		table_gfn = gpte_to_gfn(gw->ptes[level - 1]);
+		access &= gw->pte_access;
 	} else {
 		metaphysical = 0;
 		table_gfn = gw->table_gfn[level - 2];
-- 
1.7.0.3