linux-kernel - Re: [tip:x86/asm] x86/xor: Make virtualization friendly

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Message-ID: <20130126121051.GF13445@gmail.com>
Date:	Sat, 26 Jan 2013 13:10:51 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, konrad.wilk@...cle.com,
	torvalds@...ux-foundation.org, JBeulich@...e.com,
	tglx@...utronix.de, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/asm] x86/xor: Make virtualization friendly


* H. Peter Anvin <hpa@...or.com> wrote:

> On 01/25/2013 02:11 PM, H. Peter Anvin wrote:
> > On 01/25/2013 02:43 AM, tip-bot for Jan Beulich wrote:
> >> Commit-ID:  05fbf4d6fc6a3c0c3e63b77979c9311596716d10
> >> Gitweb:     http://git.kernel.org/tip/05fbf4d6fc6a3c0c3e63b77979c9311596716d10
> >> Author:     Jan Beulich <JBeulich@...e.com>
> >> AuthorDate: Fri, 2 Nov 2012 14:21:23 +0000
> >> Committer:  Ingo Molnar <mingo@...nel.org>
> >> CommitDate: Fri, 25 Jan 2013 09:23:51 +0100
> >>
> >> x86/xor: Make virtualization friendly
> >>
> >> In virtualized environments, the CR0.TS management needed here
> >> can be a lot slower than anticipated by the original authors of
> >> this code, which particularly means that in such cases forcing
> >> the use of SSE- (or MMX-) based implementations is not desirable
> >> - actual measurements should always be done in that case.
> >>
> >> For consistency, pull into the shared (32- and 64-bit) header
> >> not only the inclusion of the generic code, but also that of the
> >> AVX variants.
> >>
> > 
> > This patch is wrong and should be dropped.  I verified it with the KVM
> > people that they do NOT want this change.  It is a Xen-specific problem.
> > 
> 
> FWIW: I have dropped this patch from tip:x86/asm.

Thanks - and the other two patches are fine, right?

	Ingo
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