Re: [PATCH 2/3] drm/i915: Detect page faults during hangcheck

From: Daniel Vetter <daniel@ffwll.ch>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	Daniel Vetter <daniel@ffwll.ch>,
	Mika Kuoppala <mika.kuoppala@linux.intel.com>,
	intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/3] drm/i915: Detect page faults during hangcheck
Date: Tue, 17 Mar 2015 11:31:16 +0100	[thread overview]
Message-ID: <20150317103116.GW21993@phenom.ffwll.local> (raw)
In-Reply-To: <20150316213044.GA8591@nuc-i3427.alporthouse.com>

On Mon, Mar 16, 2015 at 09:30:44PM +0000, Chris Wilson wrote:
> On Mon, Mar 16, 2015 at 06:53:40PM +0100, Daniel Vetter wrote:
> > On Mon, Mar 16, 2015 at 03:46:35PM +0200, Mika Kuoppala wrote:
> > > From: Chris Wilson <chris@chris-wilson.co.uk>
> > > 
> > > On Sandybridge+, the GPU provides the ERROR register for detecting page
> > > faults. Hook this up to our hangcheck so that we can dump the error
> > > state soon after such an event occurs. This would be better inside an
> > > interrupt handler, but it serves a purpose here as it detects that our
> > > initial context setup is invalid...
> > > 
> > > Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
> > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > > ---
> > >  drivers/gpu/drm/i915/i915_irq.c     | 5 +++++
> > >  drivers/gpu/drm/i915/intel_uncore.c | 2 ++
> > >  2 files changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > > index 49ad5fb..ea668fc 100644
> > > --- a/drivers/gpu/drm/i915/i915_irq.c
> > > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > > @@ -2929,6 +2929,11 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
> > >  	if (!i915.enable_hangcheck)
> > >  		return;
> > >  
> > > +	if (INTEL_INFO(dev_priv)->gen >= 6 && I915_READ(ERROR_GEN6)) {
> > > +		i915_handle_error(dev, false, "GPU reported a page fault");
> > > +		I915_WRITE(ERROR_GEN6, 0);
> > 
> > Shouldn't we also at least report the bits from the ERROR register
> > somewhere? Or are they supremely useless?
> 
> It's recorded in the hangcheck already - that's how I knew we were
> generating pagefaults during module init in the first place.

Ah right missed that, so I think we're covered. Maybe a comment that
handle_error captures ERROR_GEN6? Doesn't really need to be though, just
in case someone decides to reorder the clearing with the handling.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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