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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4CADD73B.8070809@zytor.com>
Date:	Thu, 07 Oct 2010 07:20:43 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	mingo@...e.hu, Hans.Rosenfeld@....com, robert.richter@....com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	Andreas.Herrmann3@....com, peterz@...radead.org,
	fweisbec@...il.com, rostedt@...dmis.org, acme@...hat.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, eranian@...il.com
Subject: Re: [RFC 0/3] Basic support for LWP

On 10/07/2010 07:11 AM, Stephane Eranian wrote:
> On Thu, Oct 7, 2010 at 3:59 PM, H. Peter Anvin <hpa@...or.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.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/