Re: [PATCH] Lazy FPU save/restore

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Anthony Liguori wrote:
> Avi Kivity wrote:
>> Avi Kivity wrote:
>>>>
>>>> I'll have to try and setup a 64 bit system.  I cannot reproduce on 
>>>> my 32bit system with your test program.
>>>
>>> It may be related to 64-bit (as that uses sse for floating point), 
>>> or to the fact that I use ssh on a remote host, which causes more 
>>> context switches.  I'll try to reproduce on 32 bits with my setup.
>>>
>>
>> It doesn't reproduce on a 32-bit host.  However, it does reproduce on 
>> a 32-bit guest on a 64-bit host, and on a 32-bit user load running in 
>> a 64-bit guest on a 64-bit host.
>
> Thanks, I'll setup a 64 bit partition and start debugging.  I'm a bit 
> confused though, I thought CR0.TS even covers SIMD instructions?

It does, and the fact that a 32-bit guest suffers from the same issue 
indicate that sse is not the cause.

Locking the vcpu to a cpu does not change the failures, so it isn't 
related to vcpu migration.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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