[Intel-gfx] [PATCH 5/6] drm/i915: Don't use scratch in WA batch.

[Chris Wilson]

Quoting Chris Wilson (2019-09-26 11:24:35)
> Quoting Michał Winiarski (2019-09-26 11:06:34)
> > We're currently doing one workaround where we're using scratch as a
> > temporary storage place, while we're overwriting the value of one
> > register with some known constant value in order to perform a
> > workaround.
> > While we could just do similar thing with CS_GPR register
> > and MI_LOAD_REGISTER_REG instead of scratch, since we would use CS_GPR
> > anyways, let's just drop the constant values and do the bitops using
> > MI_MATH.
> 
> I'd like to have your confirmation that the w/a batch is executed before
> the CS_GPR are restored from the context image, and I'm going to wait
> for gem_ctx_isolation verification :-p

Bad news. It failed a check that CS_GPR was preserved across a context
switch on Broadwell.
-Chris