linux-kernel - [patch 147/176] KVM: MMU: Fix 32 bit legacy paging with NPT

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Date:	Tue, 15 Feb 2011 16:21:55 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org, greg@...ah.com,
	avi@...hat.com, mtosatti@...hat.com
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Joerg Roedel <joerg.roedel@....com>
Subject: [patch 147/176] KVM: MMU: Fix 32 bit legacy paging with NPT

2.6.36-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Joerg Roedel <joerg.roedel@....com>

commit f87f928882d080eaec8b0d76aecff003d664697d upstream.

This patch fixes 32 bit legacy paging with NPT enabled. The
mmu_check_root call on the top-level of the loop causes
root_gfn to take values (in the tdp_enabled path) which are
outside of guest memory. So the mmu_check_root call fails at
some point in the loop interation causing the guest to
tiple-fault.
This patch changes the mmu_check_root calls to the places
where they are really necessary. As a side-effect it
introduces a check for the root of a pae page table too.

Signed-off-by: Joerg Roedel <joerg.roedel@....com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kvm/mmu.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2254,6 +2254,10 @@ static int mmu_alloc_roots(struct kvm_vc
 		return 0;
 	}
 	direct = !is_paging(vcpu);
+
+	if (mmu_check_root(vcpu, root_gfn))
+		return 1;
+
 	for (i = 0; i < 4; ++i) {
 		hpa_t root = vcpu->arch.mmu.pae_root[i];
 
@@ -2265,10 +2269,10 @@ static int mmu_alloc_roots(struct kvm_vc
 				continue;
 			}
 			root_gfn = pdptr >> PAGE_SHIFT;
+			if (mmu_check_root(vcpu, root_gfn))
+				return 1;
 		} else if (vcpu->arch.mmu.root_level == 0)
 			root_gfn = 0;
-		if (mmu_check_root(vcpu, root_gfn))
-			return 1;
 		if (tdp_enabled) {
 			direct = 1;
 			root_gfn = i << (30 - PAGE_SHIFT);


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