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From 567b1bbf982637ce3f0ac8597af91ae8106648c8 Mon Sep 17 00:00:00 2001
From: Xiao Guangrong <>
Date: Wed, 30 Jun 2010 16:02:45 +0800
Subject: [PATCH] KVM: MMU: fix conflict access permissions in direct sp

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:
      / PDE1 -> |---|
  P[W]          |   | LPA
      \ PDE2 -> |---|

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 <>
Signed-off-by: Marcelo Tosatti <>
Signed-off-by: Avi Kivity <>
 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 ede2131..b473c0f 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -336,6 +336,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 			/* advance table_gfn when emulating 1gb pages with 4k */
 			if (delta == 0)
 				table_gfn += PT_INDEX(addr, level);
+			access &= gw->pte_access;
 		} else {
 			direct = 0;
 			table_gfn = gw->table_gfn[level - 2];