linux-kernel - Re: [GIT PULL] perf changes for v3.8

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: <50C95A21.1010101@gmail.com>
Date:	Wed, 12 Dec 2012 21:31:29 -0700
From:	David Ahern <dsahern@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] perf changes for v3.8

On 12/12/12 8:51 PM, Linus Torvalds wrote:
> SO WHY DON'T YOU JUST DO THAT THEN?
>
> Disable PEBS on Vt-x enter and re-enable it on exit. End of story.
> Exactly like you say.

See commit 26a4f3c0. But that was not enough. Requiring exclude_guest 
was another required piece. If you want to see the discussion: 
https://lkml.org/lkml/2012/7/9/264

>
> But doing it this way was wrong. Switch that "exclude_guest" attribute
> around, and admit that "H" was bogus, and that the right thing to do
> was to add a "V" flag that sets the "force_guest" flag instead.

I understand this is annoying. Older binaries on newer kernels was the 
only case I could not fix. (I guess a message could be added kernel side 
to at least give a hint.) But the alternative -- based on code that has 
existed for some time -- is for older binaries to crash VMs.

David

--
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/