[Intel-gfx] [PATCH 1/9] drm/i915/gt: Sanitize GT first

[Andi Shyti]

Hi Chris,

> We see that if the HW doesn't actually sleep, the HW may eat the poison
> we set in its write-only HWSP during sanitize:
> 
>   intel_gt_resume.part.8: 0000:00:02.0
>   __gt_unpark: 0000:00:02.0
>   gt_sanitize: 0000:00:02.0 force:yes
>   process_csb: 0000:00:02.0 vcs0: cs-irq head=5, tail=90
>   process_csb: 0000:00:02.0 vcs0: csb[0]: status=0x5a5a5a5a:0x5a5a5a5a
>   assert_pending_valid: Nothing pending for promotion!
> 
> The CS TAIL pointer should have been reset by reset_csb_pointers(), so
> in this case it is likely that we have read back from the CPU cache and
> so we must clflush our control over that page. In doing so, push the
> sanitisation to the start of the GT sequence so that our poisoning is
> assuredly before we start talking to the HW.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Reviewed-by: Andi Shyti <andi.shyti at intel.com>

Andi