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

[Stephane Eranian]

On Fri, Mar 15, 2013 at 9:53 PM, Shuah Khan <shuahkhan@xxxxxxxxx> wrote:
> On Fri, Mar 15, 2013 at 2:31 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxx>
>>> Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx>
>>> ---
>>
>> 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.
>
Testing the patch is easy:

# echo mem >/sys/power/state
Then press the power button again, when you get control again, type:

$ taskset -c 0 perf record -e cycles:pp my_test_program

Note that this problem impacts only Intel processors after Core 2
(PEBS enabled).
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