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 <ch...@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuopp...@linux.intel.com>
Cc: Akeem G Abodunrin <akeem.g.abodun...@intel.com>
---
 drivers/gpu/drm/i915/gt/gen7_renderclear.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/gen7_renderclear.c 
b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
index 56bdcdaa9a88..9b52895b23e9 100644
--- a/drivers/gpu/drm/i915/gt/gen7_renderclear.c
+++ b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
@@ -390,6 +390,13 @@ static void emit_batch(struct i915_vma * const vma,
                                                     &cb_kernel_ivb,
                                                     desc_count);
 
+       gen7_emit_pipeline_flush(&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_invalidate(&cmds);
        batch_add(&cmds, PIPELINE_SELECT | PIPELINE_SELECT_MEDIA);
        batch_add(&cmds, MI_NOOP);
-- 
2.20.1

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