[Intel-gfx] [PATCH v2] drm/i915: Exclude low pages (128KiB) of stolen from use

[Ville Syrjälä]

On Thu, Oct 08, 2020 at 11:12:37AM +0100, Chris Wilson wrote:
> Quoting Ville Syrjälä (2020-10-08 11:04:22)
> > On Thu, Oct 08, 2020 at 10:54:36AM +0100, Chris Wilson wrote:
> > > The GPU is trashing the low pages of its reserved memory upon reset. If
> > > we are using this memory for ringbuffers, then we will dutiful resubmit
> > > the trashed rings after the reset causing further resets, and worse. We
> > > must exclude this range from our own use. The value of 128KiB was found
> > > by empirical measurement on gen9.
> > > 
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > Cc: stable at vger.kernel.org
> > > ---
> > > v2 comes with a selftest to see how widespread the issue is
> > 
> > Do we need something to make sure FBC isn't scribbling into
> > stolen during the test?
> 
> igt runs the tests with disable_display=1, that is still being honoured
> right?

It just marks all connectors as disconnected now. If coming straight
from boot presumaly whatever the BIOS lit up could still be on at that
point. Though I guess we would have typically done a module reload
for this? rmmod should shut things down IIRC. Also wouldn't think the
BIOS would even enables FBC.

> 
> I did think about looking up the address to see if the drm_mm_node is in
> use to try and filter out such users. For starters, I just want to
> confirm that CI is seeing what I'm seeing.
> -Chris

-- 
Ville Syrjälä
Intel