[PATCH 1/1] drm/i915/gen9: Clear residual context state on context switch

[Tyler Hicks]

From: Akeem G Abodunrin <akeem.g.abodunrin at intel.com>

Intel GPU Hardware prior to Gen11 does not clear EU state
during a context switch. This can result in information
leakage between contexts.

For Gen8 and Gen9, hardware provides a mechanism for
fast cleardown of the EU state, by issuing a PIPE_CONTROL
with bit 27 set. We can use this in a context batch buffer
to explicitly cleardown the state on every context switch.

As this workaround is already in place for gen8, we can borrow
the code verbatim for Gen9.

Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin at intel.com>

CVE-2019-14615

(backported from commit bc8a76a152c5f9ef3b48104154a65a68a8b76946)
[tyhicks: Backport to 4.4:
 - Apply patch to i915_bpo driver since it handles gen9 chips
 - Use (i915_scratch_offset(engine->i915) + 2 * CACHELINE_BYTES) in
   place of LRC_PPHWSP_SCRATCH_ADDR and PIPE_CONTROL_GLOBAL_GTT_IVB in
   place of PIPE_CONTROL_STORE_DATA_INDEX since we're missing commit
   e1237523749e ("drm/i915/execlists: Use per-process HWSP as scratch")
 - Remove unused dev_priv variable
 - Replace the existing WaClearSlmSpaceAtContextSwitch that was being
   used for pre-production Kaby Lake]
Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
 ubuntu/i915/intel_lrc.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/ubuntu/i915/intel_lrc.c b/ubuntu/i915/intel_lrc.c
index 7f2d8415ed8b..48030b480139 100644
--- a/ubuntu/i915/intel_lrc.c
+++ b/ubuntu/i915/intel_lrc.c
@@ -1275,8 +1275,8 @@ static int gen9_init_indirectctx_bb(struct intel_engine_cs *engine,
 {
 	int ret;
 	struct drm_device *dev = engine->dev;
-	struct drm_i915_private *dev_priv = dev->dev_private;
 	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
+	uint32_t scratch_addr;
 
 	/* WaDisableCtxRestoreArbitration:skl,bxt */
 	if (IS_SKL_REVID(dev, 0, SKL_REVID_D0) ||
@@ -1289,22 +1289,18 @@ static int gen9_init_indirectctx_bb(struct intel_engine_cs *engine,
 		return ret;
 	index = ret;
 
-	/* WaClearSlmSpaceAtContextSwitch:kbl */
-	/* Actual scratch location is at 128 bytes offset */
-	if (IS_KBL_REVID(dev_priv, 0, KBL_REVID_A0)) {
-		uint32_t scratch_addr
-			= engine->scratch.gtt_offset + 2*CACHELINE_BYTES;
-
-		wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
-		wa_ctx_emit(batch, index, (PIPE_CONTROL_FLUSH_L3 |
-					   PIPE_CONTROL_GLOBAL_GTT_IVB |
-					   PIPE_CONTROL_CS_STALL |
-					   PIPE_CONTROL_QW_WRITE));
-		wa_ctx_emit(batch, index, scratch_addr);
-		wa_ctx_emit(batch, index, 0);
-		wa_ctx_emit(batch, index, 0);
-		wa_ctx_emit(batch, index, 0);
-	}
+	/* WaClearSlmSpaceAtContextSwitch:skl,bxt,kbl,glk,cfl */
+	scratch_addr = engine->scratch.gtt_offset + 2*CACHELINE_BYTES;
+	wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
+	wa_ctx_emit(batch, index, (PIPE_CONTROL_FLUSH_L3 |
+				   PIPE_CONTROL_GLOBAL_GTT_IVB |
+				   PIPE_CONTROL_CS_STALL |
+				   PIPE_CONTROL_QW_WRITE));
+	wa_ctx_emit(batch, index, scratch_addr);
+	wa_ctx_emit(batch, index, 0);
+	wa_ctx_emit(batch, index, 0);
+	wa_ctx_emit(batch, index, 0);
+
 	/* Pad to end of cacheline */
 	while (index % CACHELINE_DWORDS)
 		wa_ctx_emit(batch, index, MI_NOOP);
-- 
2.17.1