linux-kernel - Re: [PATCH] perf,x86: fix kernel crash with PEBS/BTS after suspend/resume

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Message-ID: <CAKocOOMkLwLAjF9GpbY7QFe2SvcDpWwD7Oqi213fAeu0yUaFpA@mail.gmail.com>
Date:	Fri, 15 Mar 2013 14:53:35 -0600
From:	Shuah Khan <shuahkhan@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	peterz@...radead.org, mingo@...e.hu, tglx@...utronix.de,
	akpm@...ux-foundation.org, acme@...hat.com, jolsa@...hat.com,
	ak@...ux.intel.com
Subject: Re: [PATCH] perf,x86: fix kernel crash with PEBS/BTS after suspend/resume

On Fri, Mar 15, 2013 at 2:31 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Fri, Mar 15, 2013 at 02:26:07PM +0100, Stephane Eranian wrote:
>>
>> This patch fixes a kernel crash when using precise sampling (PEBS)
>> after a suspend/resume. Turns out the CPU notifier code is not invoked
>> on CPU0 (BP). Therefore, the DS_AREA (used by PEBS) is not restored properly
>> by the kernel and keeps it power-on/resume value of 0 causing any PEBS
>> measurement to crash when running on CPU0.
>>
>> The workaround is to add a hook in the actual resume code to restore
>> the DS Area MSR value. It is invoked for all CPUS. So for all but CPU0,
>> the DS_AREA will be restored twice but this is harmless.
>>
>> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
>> Signed-off-by: Stephane Eranian <eranian@...gle.com>
>> ---
>
> Is this needed for the 3.8 or older kernels as well?
>
> thanks,
>
> greg k-h

Just about to ask the same question. Patch applies to 3.8, 3.4, 3.2
and 3.5. But needs some massaging for 3.0. I have the kernels built,
haven't started testing yet.

-- Shuah
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