linux-kernel - [PATCH 4.2.y-ckt 257/305] KVM: MTRR: fix fixed MTRR segment look up

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Message-Id: <1452902519-2754-258-git-send-email-kamal@canonical.com>
Date:	Fri, 15 Jan 2016 16:01:11 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Alexis Dambricourt <alexis.dambricourt@...il.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 257/305] KVM: MTRR: fix fixed MTRR segment look up

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Alexis Dambricourt <alexis.dambricourt@...il.com>

commit a7f2d7865720ff13d5b0f2a3bb1fd80dc3d7a73f upstream.

This fixes the slow-down of VM running with pci-passthrough, since some MTRR
range changed from MTRR_TYPE_WRBACK to MTRR_TYPE_UNCACHABLE.  Memory in the
0K-640K range was incorrectly treated as uncacheable.

Fixes: f7bfb57b3e89ff89c0da9f93dedab89f68d6ca27
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=107561
Signed-off-by: Alexis Dambricourt <alexis.dambricourt@...il.com>
[Use correct BZ for "Fixes" annotation.  - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/x86/kvm/mtrr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index 9e8bf13..adc54e1 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -267,7 +267,7 @@ static int fixed_mtrr_addr_to_seg(u64 addr)
 
 	for (seg = 0; seg < seg_num; seg++) {
 		mtrr_seg = &fixed_seg_table[seg];
-		if (mtrr_seg->start >= addr && addr < mtrr_seg->end)
+		if (mtrr_seg->start <= addr && addr < mtrr_seg->end)
 			return seg;
 	}
 
-- 
1.9.1