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

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Date:	Fri, 15 Mar 2013 13:56:59 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>,
	"ak@...ux.intel.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 09:49:00PM +0100, Stephane Eranian wrote:
> On Fri, Mar 15, 2013 at 9:31 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?
> >
> I suspect so. If CPU0 is not covered by the cpu notifiers
> then yes, the patch is needed.

Ok, thanks, I've queued it up now there.

greg k-h
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