From: "H. Peter Anvin" <hpa@zytor.com>
To: Vincent Palatin <vpalatin@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
Jarkko Sakkinen <jarkko.sakkinen@intel.com>,
Duncan Laurie <dlaurie@chromium.org>,
Olof Johansson <olofj@chromium.org>
Subject: Re: [PATCH] x86, fpu: avoid FPU lazy restore after suspend
Date: Fri, 30 Nov 2012 10:57:05 -0800 [thread overview]
Message-ID: <50B90181.4070705@zytor.com> (raw)
In-Reply-To: <1354301523-5252-2-git-send-email-vpalatin@chromium.org>
On 11/30/2012 10:52 AM, Vincent Palatin wrote:
> When a cpu enters S3 state, the FPU state is lost.
> After resuming for S3, if we try to lazy restore the FPU for a process running
> on the same CPU, this will result in a corrupted FPU context.
>
> We can just invalidate the "fpu_owner_task", so nobody will try to
> lazy restore a state which no longer exists in the hardware.
>
> Tested with a 64-bit kernel on a 4-core Ivybridge CPU with eagerfpu=off,
> by doing thousands of suspend/resume cycles with 4 processes doing FPU
> operations running. Without the patch, a process is killed after a
> few hundreds cycles by a SIGFPE.
>
> The issue seems to exist since 3.4 (after the FPU lazy restore was actually implemented),
> to apply the change to 3.4, "this_cpu_write" needs to be replaced by percpu_write.
>
> Cc: Duncan Laurie <dlaurie@chromium.org>
> Cc: Olof Johansson <olofj@chromium.org>
> Cc: <stable@kernel.org> [v3.4+] # for 3.4 need to replace this_cpu_write by percpu_write
> Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
Ouch! Thank you for catching this!
-hpa
next prev parent reply other threads:[~2012-11-30 18:57 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-30 18:52 issue with x86 FPU state after suspend to ram Vincent Palatin
2012-11-30 18:52 ` [PATCH] x86, fpu: avoid FPU lazy restore after suspend Vincent Palatin
2012-11-30 18:57 ` H. Peter Anvin [this message]
2012-11-30 19:25 ` Linus Torvalds
2012-11-30 19:38 ` H. Peter Anvin
2012-11-30 19:41 ` Linus Torvalds
2012-11-30 19:51 ` H. Peter Anvin
[not found] ` <CAP_ceTxmMhQeDi=x9HmYke85hKMg3_YhbXSnfDC12rOcocQJpA@mail.gmail.com>
2012-11-30 19:55 ` H. Peter Anvin
2012-11-30 21:45 ` Vincent Palatin
2012-11-30 19:52 ` [PATCH v2] " Vincent Palatin
2012-11-30 20:15 ` [PATCH v3] " Vincent Palatin
2012-11-30 22:10 ` [tip:x86/urgent] x86, fpu: Avoid " tip-bot for Vincent Palatin
2012-11-30 19:26 ` tip-bot for Vincent Palatin
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