Re: [RFC 0/3] Basic support for LWP

[Stephane Eranian]

On Thu, Oct 7, 2010 at 4:20 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 10/07/2010 07:11 AM, Stephane Eranian wrote:
>> On Thu, Oct 7, 2010 at 3:59 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>>> On 10/07/2010 03:46 AM, Stephane Eranian wrote:
>>>>
>>>> As for the patch itself, I am not an expert at xsave/xrstor, but it seems to
>>>> me you could decouple LWP from FPU. I think ÂBrian had the same comment.
>>>> I suspect this can be done and it will certainly look cleaner.
>>>>
>>>
>>> Well, once you're using XSAVE you're not decoupled from the FPU. ÂWorse,
>>> if you're using XSAVE and not honoring CR0.TS you have a major design flaw.
>>>
>> Is that to say, that if you use LWP you will have to save/restore FPU state even
>> though you're not actually using it?
>>
>
> No, but you wouldn't be able to use lazy FPU.
>
You mean lazy restore, I am guessing here.
Is that to say, you cannot figure out whether the FPU state in
the CPU on ctxsw in is yours anymore?

> Â Â Â Â-hpa
>
> --
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel. ÂI don't speak on their behalf.
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/