From d203f9a175bbddae6d69d58819fdd0cc87ac58e6 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 11 Feb 2020 20:56:15 +0000
Subject: drm/i915/selftests: Sabotague the RING_HEAD
Git-commit: 37305ede63c7e5a696b74b64ffb7c62cbe0ecd2f
Patch-mainline: v5.7-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
Apply vast quantities of poison and not tell anyone to see if we fall
for the trap of using a stale RING_HEAD.
References: 42827350f75c ("drm/i915/gt: Avoid resetting ring->head outside of its timeline mutex")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211205615.1190127-2-chris@chris-wilson.co.uk
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/gt/selftest_lrc.c | 79 ++++++++++++++++++++++++++
1 file changed, 79 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
index e53bfedeb97e..26d39c111d16 100644
--- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
@@ -300,6 +300,84 @@ static int live_unlite_preempt(void *arg)
return live_unlite_restore(arg, I915_USER_PRIORITY(I915_PRIORITY_MAX));
}
+static int live_pin_rewind(void *arg)
+{
+ struct intel_gt *gt = arg;
+ struct intel_engine_cs *engine;
+ enum intel_engine_id id;
+ int err = 0;
+
+ /*
+ * We have to be careful not to trust intel_ring too much, for example
+ * ring->head is updated upon retire which is out of sync with pinning
+ * the context. Thus we cannot use ring->head to set CTX_RING_HEAD,
+ * or else we risk writing an older, stale value.
+ *
+ * To simulate this, let's apply a bit of deliberate sabotague.
+ */
+
+ for_each_engine(engine, gt, id) {
+ struct intel_context *ce;
+ struct i915_request *rq;
+ struct intel_ring *ring;
+ struct igt_live_test t;
+
+ if (igt_live_test_begin(&t, gt->i915, __func__, engine->name)) {
+ err = -EIO;
+ break;
+ }
+
+ ce = intel_context_create(engine);
+ if (IS_ERR(ce)) {
+ err = PTR_ERR(ce);
+ break;
+ }
+
+ err = intel_context_pin(ce);
+ if (err) {
+ intel_context_put(ce);
+ break;
+ }
+
+ /* Keep the context awake while we play games */
+ err = i915_active_acquire(&ce->active);
+ if (err) {
+ intel_context_unpin(ce);
+ intel_context_put(ce);
+ break;
+ }
+ ring = ce->ring;
+
+ /* Poison the ring, and offset the next request from HEAD */
+ memset32(ring->vaddr, STACK_MAGIC, ring->size / sizeof(u32));
+ ring->emit = ring->size / 2;
+ ring->tail = ring->emit;
+ GEM_BUG_ON(ring->head);
+
+ intel_context_unpin(ce);
+
+ /* Submit a simple nop request */
+ GEM_BUG_ON(intel_context_is_pinned(ce));
+ rq = intel_context_create_request(ce);
+ i915_active_release(&ce->active); /* e.g. async retire */
+ intel_context_put(ce);
+ if (IS_ERR(rq)) {
+ err = PTR_ERR(rq);
+ break;
+ }
+ GEM_BUG_ON(!rq->head);
+ i915_request_add(rq);
+
+ /* Expect not to hang! */
+ if (igt_live_test_end(&t)) {
+ err = -EIO;
+ break;
+ }
+ }
+
+ return err;
+}
+
static int live_hold_reset(void *arg)
{
struct intel_gt *gt = arg;
@@ -3629,6 +3707,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
SUBTEST(live_sanitycheck),
SUBTEST(live_unlite_switch),
SUBTEST(live_unlite_preempt),
+ SUBTEST(live_pin_rewind),
SUBTEST(live_hold_reset),
SUBTEST(live_error_interrupt),
SUBTEST(live_timeslice_preempt),
--
2.28.0