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

Eric Dumazet
2011-08-22T06:45:11Z

Le lundi 22 août 2011 à 09:36 +0300, Avi Kivity a écrit :
> On 08/20/2011 04:16 PM, Brad Campbell wrote:
> > Author: Alexander Duyck <alexander.h.duyck@intel.com>
> > 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@linux.intel.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: x86@kernel.org
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
> > Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> > Acked-by: H. Peter Anvin <hpa@zytor.com>
> > Signed-off-by: David S. Miller <davem@davemloft.net>
> >
> > :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.
>

Some piece of hardware has a 2-byte offset requirement, and driver
incorrectly assumed NET_IP_ALIGN was 2 on x86.

Brad, could you post your config (lsmod, dmesg) again ?

tg3.c code for example uses a private value, not related to NET_IP_ALIGN

#define TG3_RAW_IP_ALIGN 2