From: Benjamin LaHaise <bcrl@kvack.org>
To: Andi Kleen <ak@suse.de>
Cc: Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@osdl.org>,
Chuck Ebbert <76306.1226@compuserve.com>,
In Cognito <defend.the.world@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: Sysenter crash with Nested Task Bit set
Date: Mon, 18 Sep 2006 12:12:51 -0400 [thread overview]
Message-ID: <20060918161251.GC19815@kvack.org> (raw)
In-Reply-To: <200609181729.23934.ak@suse.de>
On Mon, Sep 18, 2006 at 05:29:23PM +0200, Andi Kleen wrote:
> > - asm volatile("pushl %%ebp\n\t" \
> > + asm volatile("pushfl\n\t" /* Save flags */ \
> > + "pushl %%ebp\n\t" \
>
> We used to do that pushfl/popfl some time ago, but Ben removed it because
> it was slow on P4. Ok, nobody thought of that case back then.
It's the pushfl that will be slow on any OoO CPU, as it has dependancies on
any previous instructions that modified the flags, which ends up bringing
all of the memory ordering dependancies into play. Doing a popfl to set the
flags to some known value is much less expensive.
-ben
--
"Time is of no importance, Mr. President, only life is important."
Don't Email: <dont@kvack.org>.
next prev parent reply other threads:[~2006-09-18 16:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-18 3:51 Sysenter crash with Nested Task Bit set Chuck Ebbert
2006-09-18 5:25 ` Andrew Morton
2006-09-18 8:44 ` Mike Galbraith
2006-09-18 15:11 ` Linus Torvalds
2006-09-18 15:06 ` Ingo Molnar
2006-09-18 15:29 ` Andi Kleen
2006-09-18 15:24 ` Ingo Molnar
2006-09-18 16:02 ` Linus Torvalds
2006-09-18 16:10 ` Linus Torvalds
2006-09-18 16:24 ` Jeremy Fitzhardinge
2006-09-18 16:12 ` Benjamin LaHaise [this message]
2006-09-18 16:39 ` Andi Kleen
2006-09-18 19:01 ` Jeremy Fitzhardinge
[not found] <5a20704e0609171603s55ca52bap71dc2fa2c05d6741@mail.gmail.com>
2006-09-17 23:08 ` In Cognito
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