[Intel-gfx] [PATCH] drm/i915/gt: Clear CACHE_MODE prior to clearing residuals

[Abodunrin, Akeem G]

> -----Original Message-----
> From: Chris Wilson <chris at chris-wilson.co.uk>
> Sent: Sunday, January 17, 2021 1:30 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Chris Wilson <chris at chris-wilson.co.uk>; Mika Kuoppala
> <mika.kuoppala at linux.intel.com>; Abodunrin, Akeem G
> <akeem.g.abodunrin at intel.com>
> Subject: [PATCH] drm/i915/gt: Clear CACHE_MODE prior to clearing residuals
> 
> Since we do a bare context switch with no restore, the clear residual kernel
> runs on dirty state, and we must be careful to avoid executing bad state from
> context registers inherited from a malicious client.
> 
> Fixes: 008ead6ef8f5 ("drm/i915/gt: Restore clear-residual mitigations for
> Ivybridge, Baytrail")
> Fixes: 09aa9e45863e ("drm/i915/gt: Restore clear-residual mitigations for
> Ivybridge, Baytrail")
> Testcase: igt/gem_ctx_isolation # ivb,vlv
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Akeem G Abodunrin <akeem.g.abodunrin at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/gen7_renderclear.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> index 56bdcdaa9a88..0490c29788d7 100644
> --- a/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> +++ b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> @@ -390,6 +390,14 @@ static void emit_batch(struct i915_vma * const
> vma,
>  						     &cb_kernel_ivb,
>  						     desc_count);
> 
> +	gen7_emit_pipeline_invalidate(&cmds);
> +	batch_add(&cmds, MI_LOAD_REGISTER_IMM(2));
> +	batch_add(&cmds, i915_mmio_reg_offset(CACHE_MODE_0_GEN7));
> +	batch_add(&cmds, 0xffff0000);
> +	batch_add(&cmds, i915_mmio_reg_offset(CACHE_MODE_1));
> +	batch_add(&cmds, 0xffff0000 |
> PIXEL_SUBSPAN_COLLECT_OPT_DISABLE);
> +	gen7_emit_pipeline_flush(&cmds);
> +
>  	gen7_emit_pipeline_invalidate(&cmds);
>  	batch_add(&cmds, PIPELINE_SELECT | PIPELINE_SELECT_MEDIA);
>  	batch_add(&cmds, MI_NOOP);
> --
> 2.20.1

Reviewed-by: Akeem G Abodunrin <akeem.g.abodunrin at intel.com>

Thanks,
~Akeem