[3.13.y.z extended stable] Patch "Revert "KVM: x86: Increase the number of fixed MTRR regs to 10"" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Tue Sep 30 21:29:28 UTC 2014

This is a note to let you know that I have just added a patch titled

    Revert "KVM: x86: Increase the number of fixed MTRR regs to 10"

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see



>From 2dd51850e6924ffc4a1d512261946cecff8fda6d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini at redhat.com>
Date: Mon, 18 Aug 2014 16:39:48 +0200
Subject: Revert "KVM: x86: Increase the number of fixed MTRR regs to 10"

commit 0d234daf7e0a3290a3a20c8087eefbd6335a5bd4 upstream.

This reverts commit 682367c494869008eb89ef733f196e99415ae862,
which causes 32-bit SMP Windows 7 guests to panic.

SeaBIOS has a limit on the number of MTRRs that it can handle,
and this patch exceeded the limit.  Better revert it.
Thanks to Nadav Amit for debugging the cause.

Reported-by: Wanpeng Li <wanpeng.li at linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 arch/x86/include/asm/kvm_host.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c16aef8..2122ffb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -99,7 +99,7 @@ static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
 #define KVM_REFILL_PAGES 25
-#define KVM_NR_VAR_MTRR 10
+#define KVM_NR_VAR_MTRR 8

 #define ASYNC_PF_PER_VCPU 64


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