Re: [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP

Jan Kiszka
2011-06-15T11:45:48Z

On 2011-06-15 13:33, Avi Kivity wrote:
> On 06/15/2011 02:32 PM, Jan Kiszka wrote:
>>>
>>> If it isn't zero, there's still a good chance fopcode will be zero
>>> (64-bit userspace, thread that hasn't used the fpu since the last
>>> context switch, last opcode happened to be zero).
>>
>> I do not yet find "if fopcode is invalid, it is zero, just as IP and DP"
>> in the spec. What clears them reliably?
>
> FNINIT

OK, I see. So we simply check for all fields being zero and skip the
section in that case. The MSR doesn't actually to us here.

Will write v2.

Jan

--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux