From: David Ahern <dsahern@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [GIT PULL] perf changes for v3.8
Date: Wed, 12 Dec 2012 21:31:29 -0700 [thread overview]
Message-ID: <50C95A21.1010101@gmail.com> (raw)
In-Reply-To: <CA+55aFzmsEbKCg=Qp0LGxQb-D+ZfBAELEa4HyUkuxkj6Z0-agA@mail.gmail.com>
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
next prev parent reply other threads:[~2012-12-13 4:31 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-11 9:09 [GIT PULL] perf changes for v3.8 Ingo Molnar
2012-12-13 2:53 ` Linus Torvalds
2012-12-13 3:02 ` David Ahern
2012-12-13 3:09 ` Linus Torvalds
2012-12-13 3:16 ` David Ahern
2012-12-13 3:25 ` David Ahern
2012-12-13 3:34 ` Linus Torvalds
2012-12-13 3:43 ` David Ahern
2012-12-13 3:51 ` Linus Torvalds
2012-12-13 4:31 ` David Ahern [this message]
2012-12-13 4:46 ` Linus Torvalds
2012-12-13 7:27 ` Ingo Molnar
2012-12-13 7:30 ` Ingo Molnar
2012-12-13 14:30 ` David Ahern
2012-12-13 14:38 ` David Ahern
2012-12-13 16:03 ` Linus Torvalds
2012-12-13 16:24 ` David Ahern
2012-12-13 16:33 ` Linus Torvalds
2012-12-13 16:59 ` Ingo Molnar
2012-12-13 17:10 ` Linus Torvalds
2012-12-13 17:31 ` Ingo Molnar
2012-12-17 4:43 ` David Ahern
2012-12-22 19:22 ` David Ahern
2012-12-23 0:00 ` Linus Torvalds
2012-12-13 17:02 ` Linus Torvalds
2012-12-13 17:30 ` David Ahern
2012-12-13 17:36 ` Ingo Molnar
2012-12-13 19:12 ` David Ahern
2012-12-13 7:48 ` [PATCH] Revert "perf: Require exclude_guest to use PEBS - kernel side enforcement" Ingo Molnar
[not found] ` <20121217102000.GE11016@redhat.com>
2012-12-22 19:30 ` [GIT PULL] perf changes for v3.8 David Ahern
2012-12-23 9:23 ` Gleb Natapov
2012-12-23 23:17 ` David Ahern
2012-12-24 10:36 ` Gleb Natapov
2012-12-13 17:04 ` [PATCH] x86: fix perf build with uclibc toolchains Florian Fainelli
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