[Intel-gfx] [PATCH 02/12] drm/i915: BUG_ON bad PPGTT offset

[Daniel Vetter]

On Mon, May 6, 2013 at 8:03 PM, Ben Widawsky <ben at bwidawsk.net> wrote:
> On Mon, May 06, 2013 at 11:48:05AM +0200, Daniel Vetter wrote:
>> On Thu, May 02, 2013 at 01:28:23PM -0700, Jesse Barnes wrote:
>> > On Tue, 23 Apr 2013 23:15:30 -0700
>> > Ben Widawsky <ben at bwidawsk.net> wrote:
>> >
>> > > Because PPGTT PDEs within the GTT are calculated in cachelines
>> > > (HW guys consistency ftw) we do a divide which will wreak havoc if this
>> > > is wrong, and I know that from experience).
>> > >
>> > > If/when we move to multiple PPGTTs this will have to become a WARN, and
>> > > return an error. For now however it should always be considered fatal,
>> > > and only a developer could hit it.
>> > >
>> > > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
>> > > ---
>> > >  drivers/gpu/drm/i915/i915_gem_gtt.c | 2 ++
>> > >  1 file changed, 2 insertions(+)
>> > >
>> > > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
>> > > index 50df194..0503f09 100644
>> > > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
>> > > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
>> > > @@ -85,6 +85,8 @@ static int gen6_ppgtt_enable(struct drm_device *dev)
>> > >   uint32_t pd_entry;
>> > >   int i;
>> > >
>> > > + BUG_ON(ppgtt->pd_offset & 0x3f);
>> > > +
>> > >   pd_addr = (gen6_gtt_pte_t __iomem*)dev_priv->gtt.gsm +
>> > >           ppgtt->pd_offset / sizeof(gen6_gtt_pte_t);
>> > >   for (i = 0; i < ppgtt->num_pd_entries; i++) {
>> >
>> > Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>
>>
>> Queued for -next with the same s/BUG/WARN bikeshed, thanks for the patch.
>> -Daniel
>
> If you're going to change to WARN, please fixup the patch to return
> early... if (WARN_ON(...)) return
>
> The GPU will end up hanging if we've messed this up...

I don't care about the gpu, only that the logs hit the disc. And I
don't see how an early return can safe anything in here, since
something went horribly wrong already anyway.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch