Re: KVM induced panic on 2.6.38[2367] & 2.6.39

From: Avi Kivity
Date: Mon Aug 22 2011 - 02:36:31 EST


On 08/20/2011 04:16 PM, Brad Campbell wrote:
Author: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
Date: Thu Jul 1 13:28:27 2010 +0000

x86: Drop CONFIG_MCORE2 check around setting of NET_IP_ALIGN

This patch removes the CONFIG_MCORE2 check from around NET_IP_ALIGN. It is
based on a suggestion from Andi Kleen. The assumption is that there are
not any x86 cores where unaligned access is really slow, and this change
would allow for a performance improvement to still exist on configurations
that are not necessarily optimized for Core 2.

Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
Acked-by: H. Peter Anvin <hpa@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

:040000 040000 5a15867789080a2f67a74b17c4422f85b7a9fb4a b98769348bd765731ca3ff03b33764257e23226c M arch

I can confirm this bug exists in the 3.0 kernel, however I'm unable to reproduce it on todays git.

So anyone using netfilter, kvm and bridge on kernels between 2.6.36-rc1 and 3.0 may hit this bug, but it looks like it is fixed in the current 3.1-rc kernels.


Thanks for this effort. I don't think this patch is buggy in itself, it merely exposed another bug which was fixed later on.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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