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

[Shuah Khan]

On Fri, Mar 15, 2013 at 2:56 PM, Stephane Eranian <eranian@xxxxxxxxxx> wrote:
> 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).

Thanks. Reproduced the problem on 3.8.3, 3.4.36, and 3.0.69. Tested
the patch on 3.4 and 3.8 and the problem is fixed. I had to re-cut the
patch for 3.0. Sending it to stable tagged for 3.0

Thanks,
-- Shuah
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