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DateWed, 31 Mar 2010 14:11:57 +0200
FromAndre Przywara <>
SubjectRe: KVM warning about uncertified CPU for SMP for AMD model 2, stepping 3
Andi Kleen wrote:
> On Wed, Mar 31, 2010 at 01:03:02AM +0200, Jiri Kosina wrote:
>> Hi,
>>
>> booting 32bit guest on 32bit host on AMD system gives me the following
>> warning when KVM is instructed to boot as SMP:
>
> I guess these warnings could be just disabled. With nearly everyone
> using multi-core these days they are kind of obsolete anyways.
Well, the warning refers to an old single-core only CPU model. Most of
those were able to run in SMP boards, but only a subset of them was
officially certified to do so (Athlon-MP instead of Athlon-XP).
To avoid complaints about instability of such systems, the warning was
introduced. If you consider these systems still supported, I wouldn't
disable this warning, at least the check should be disabled only if the
hypervisor CPUID bit is set.

But the far better solution is to instruct QEMU/KVM to inject a better
CPU model (as it was suggested by some people two weeks ago). I am about
to test various guests with respect to their behavior regarding
different family/model/stepping settings (one issue is already fixed).
If this goes well, I will send out the patch to inject the host's CPUID
F/M/S into the guest by default (which has other advantages, but denies
migration mostly).
BTW.: I encourage people to test their KVM guests with "-cpu host" (on
newer QEMUs) and send me any crash logs.

Regards,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448-3567-12



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