From: "H. Peter Anvin" <hpa@zytor.com>
To: Stephane Eranian <eranian@google.com>
Cc: mingo@elte.hu, Hans.Rosenfeld@amd.com, robert.richter@amd.com,
tglx@linutronix.de, linux-kernel@vger.kernel.org,
Andreas.Herrmann3@amd.com, peterz@infradead.org,
fweisbec@gmail.com, rostedt@goodmis.org, acme@redhat.com,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
eranian@gmail.com
Subject: Re: [RFC 0/3] Basic support for LWP
Date: Thu, 07 Oct 2010 07:20:43 -0700 [thread overview]
Message-ID: <4CADD73B.8070809@zytor.com> (raw)
In-Reply-To: <AANLkTin+PXzz4qJHX6kHiQW8Rqdrv=hrvq4iWuaOnGiV@mail.gmail.com>
On 10/07/2010 07:11 AM, Stephane Eranian wrote:
> On Thu, Oct 7, 2010 at 3:59 PM, H. Peter Anvin <hpa@zytor.com> 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 Brian 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. Worse,
>> 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.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2010-10-07 14:22 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1286212172-654419-1-git-send-email-hans.rosenfeld@amd.com>
2010-10-04 22:13 ` [RFC 0/3] Basic support for LWP Thomas Gleixner
2010-10-05 14:51 ` Hans Rosenfeld
2010-10-05 15:34 ` Thomas Gleixner
2010-10-05 18:27 ` Hans Rosenfeld
2010-10-05 18:30 ` Hans Rosenfeld
2010-10-05 18:30 ` [RFC 1/3] Cleanup xsave/xrstor support Hans Rosenfeld
2010-10-05 18:30 ` [RFC 2/3] Allow saving of individual states in fpu_xsave() Hans Rosenfeld
2010-10-05 18:30 ` [RFC 3/3] Save/restore LWP state in context switches Hans Rosenfeld
2010-10-06 11:12 ` Brian Gerst
2010-10-07 14:58 ` Hans Rosenfeld
2010-11-23 20:41 ` [RFC 0/2] FPU/xsave rework in preparation for LWP Hans Rosenfeld
2010-11-23 20:41 ` [RFC 1/2] x86, xsave: cleanup xsave/xrstor support Hans Rosenfeld
2010-11-23 20:41 ` [RFC 2/2] x86, xsave: rework xsave support Hans Rosenfeld
2010-11-25 0:36 ` Brian Gerst
2010-10-05 19:05 ` [RFC 0/3] Basic support for LWP Ingo Molnar
2010-10-06 7:35 ` Robert Richter
[not found] ` <AANLkTi=T0QmcKeZcgcR+GKk-9OwQUB_x8XdHiNuU7tE_@mail.gmail.com>
2010-10-07 10:46 ` Stephane Eranian
2010-10-07 13:59 ` H. Peter Anvin
2010-10-07 14:11 ` Stephane Eranian
2010-10-07 14:20 ` Hans Rosenfeld
2010-10-07 14:20 ` H. Peter Anvin [this message]
2010-10-07 14:25 ` Stephane Eranian
2010-10-07 14:47 ` H. Peter Anvin
2010-10-07 15:12 ` Stephane Eranian
2010-10-05 18:43 ` Davidlohr Bueso
2010-10-06 10:26 ` Andi Kleen
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