Re: [PATCH] Lazy FPU save/restore

Avi Kivity
2007-02-19T08:13:26Z

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.