[PATCH 5.10 055/142] drm/i915/gt: Clear CACHE_MODE prior to clearing residuals

[Greg Kroah-Hartman]

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit ef99a60ffd9b918354e038bc5e61f007ff7e901d upstream.

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
with bad state from context registers inherited from a malicious client.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2955
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@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
Reviewed-by: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20210117093015.29143-1-chris@xxxxxxxxxxxxxxxxxx
(cherry picked from commit ace44e13e577c2ae59980e9a6ff5ca253b1cf831)
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/gt/gen7_renderclear.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/gpu/drm/i915/gt/gen7_renderclear.c
+++ b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
@@ -390,6 +390,16 @@ static void emit_batch(struct i915_vma *
 						     &cb_kernel_ivb,
 						     desc_count);
 
+	/* Reset inherited context registers */
+	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);
+
+	/* Switch to the media pipeline and our base address */
 	gen7_emit_pipeline_invalidate(&cmds);
 	batch_add(&cmds, PIPELINE_SELECT | PIPELINE_SELECT_MEDIA);
 	batch_add(&cmds, MI_NOOP);
@@ -399,9 +409,11 @@ static void emit_batch(struct i915_vma *
 	gen7_emit_state_base_address(&cmds, descriptors);
 	gen7_emit_pipeline_invalidate(&cmds);
 
+	/* Set the clear-residual kernel state */
 	gen7_emit_vfe_state(&cmds, bv, urb_size - 1, 0, 0);
 	gen7_emit_interface_descriptor_load(&cmds, descriptors, desc_count);
 
+	/* Execute the kernel on all HW threads */
 	for (i = 0; i < num_primitives(bv); i++)
 		gen7_emit_media_object(&cmds, i);