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

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: <510302FD.3090009@zytor.com>
Date:	Fri, 25 Jan 2013 14:11:09 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	konrad.wilk@...cle.com, torvalds@...ux-foundation.org,
	JBeulich@...e.com, jbeulich@...e.com, tglx@...utronix.de
CC:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/asm] x86/xor: Make virtualization friendly

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.

	-hpa


--
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/