Re: [Intel-gfx] [PATCH] drm/i915/guc: Fix revocation of non-persistent contexts

[Tvrtko Ursulin]

On 30/09/2022 15:52, Andrzej Hajda wrote:
On 30.09.2022 11:47, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursu...@intel.com>

Patch which added graceful exit for non-persistent contexts missed the
fact it is not enough to set the exiting flag on a context and let the
backend handle it from there.

GuC backend cannot handle it because it runs independently in the
firmware and driver might not see the requests ever again. Patch also
missed the fact some usages of intel_context_is_banned in the GuC backend
needed replacing with newly introduced intel_context_is_schedulable.

Fix the first issue by calling into backend revoke when we know this is
the last chance to do it. Fix the second issue by replacing
intel_context_is_banned with intel_context_is_schedulable, which should
always be safe since latter is a superset of the former.

negation of the latter is a ...?

I did not get what you meant here.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Fixes: 45c64ecf97ee ("drm/i915: Improve user experience and driver 
robustness under SIGINT or similar")
Cc: Andrzej Hajda <andrzej.ha...@intel.com>
Cc: John Harrison <john.c.harri...@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospu...@intel.com>
---
  drivers/gpu/drm/i915/gem/i915_gem_context.c   |  8 +-----
  drivers/gpu/drm/i915/gt/intel_context.c       | 14 +++++++---
  drivers/gpu/drm/i915/gt/intel_context.h       |  8 +-----
  .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 26 +++++++++----------
  4 files changed, 25 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c 
b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 0bcde53c50c6..1e29b1e6d186 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1387,14 +1387,8 @@ kill_engines(struct i915_gem_engines *engines, 
bool exit, bool persistent)
       */
      for_each_gem_engine(ce, engines, it) {
          struct intel_engine_cs *engine;
-        bool skip = false;
-        if (exit)
-            skip = intel_context_set_exiting(ce);
-        else if (!persistent)
-            skip = intel_context_exit_nonpersistent(ce, NULL); > -
-        if (skip)
+        if ((exit || !persistent) && intel_context_revoke(ce))
              continue; /* Already marked. */
          /*
diff --git a/drivers/gpu/drm/i915/gt/intel_context.c 
b/drivers/gpu/drm/i915/gt/intel_context.c
index 654a092ed3d6..398b2a9eed61 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -614,13 +614,19 @@ bool intel_context_ban(struct intel_context *ce, 
struct i915_request *rq)
      return ret;
  }
-bool intel_context_exit_nonpersistent(struct intel_context *ce,
-                      struct i915_request *rq)
+bool intel_context_revoke(struct intel_context *ce)
  {
      bool ret = intel_context_set_exiting(ce);
-    if (ce->ops->revoke)
-        ce->ops->revoke(ce, rq, ce->engine->props.preempt_timeout_ms);
+    if (!ret && intel_engine_uses_guc(ce->engine)) {
+        /*
+         * With GuC backend we have to notify it of revocation as soon
+         * as the exiting flag is set.
+         */
+        if (ce->ops->revoke)
+            ce->ops->revoke(ce, NULL,
+                    ce->engine->props.preempt_timeout_ms);
+    }

Now revoke is called only with GuC, previously it was called also for 
other backends in case non-exiting/non-persistent, is it OK?

It is okay (execlists has no revoke vfunc, ringbuffer has it but only 
works if target request is known), but agreed it is a bit ugly. I was in 
two minds which way to go. Perhaps it would indeed be cleaner to go 
unconditional. I will resend with that change, copying stable this time 
round (since 6.0 is out), and can keep your r-b?

Regards,

Tvrtko


      return ret;
  }
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h 
b/drivers/gpu/drm/i915/gt/intel_context.h
index 8e2d70630c49..40f8809d14ea 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -319,18 +319,12 @@ static inline bool 
intel_context_is_schedulable(const struct intel_context *ce)
             !test_bit(CONTEXT_BANNED, &ce->flags);
  }
-static inline bool intel_context_is_exiting(const struct 
intel_context *ce)
-{
-    return test_bit(CONTEXT_EXITING, &ce->flags);
-}
-
  static inline bool intel_context_set_exiting(struct intel_context *ce)
  {
      return test_and_set_bit(CONTEXT_EXITING, &ce->flags);
  }
-bool intel_context_exit_nonpersistent(struct intel_context *ce,
-                      struct i915_request *rq);
+bool intel_context_revoke(struct intel_context *ce);
  static inline bool
  intel_context_force_single_submission(const struct intel_context *ce)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c 
b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 0ef295a94060..88a4476b8e92 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -685,7 +685,7 @@ static int __guc_add_request(struct intel_guc 
*guc, struct i915_request *rq)
       * Corner case where requests were sitting in the priority list 
or a
       * request resubmitted after the context was banned.
       */
-    if (unlikely(intel_context_is_banned(ce))) {
+    if (unlikely(!intel_context_is_schedulable(ce))) {
          i915_request_put(i915_request_mark_eio(rq));
          intel_engine_signal_breadcrumbs(ce->engine);
          return 0;
@@ -871,15 +871,15 @@ static int guc_wq_item_append(struct intel_guc 
*guc,
                    struct i915_request *rq)
  {
      struct intel_context *ce = request_to_scheduling_context(rq);
-    int ret = 0;
+    int ret;
-    if (likely(!intel_context_is_banned(ce))) {
-        ret = __guc_wq_item_append(rq);
+    if (unlikely(!intel_context_is_schedulable(ce)))
+        return 0;
-        if (unlikely(ret == -EBUSY)) {
-            guc->stalled_request = rq;
-            guc->submission_stall_reason = STALL_MOVE_LRC_TAIL;
-        }
+    ret = __guc_wq_item_append(rq);
+    if (unlikely(ret == -EBUSY)) {
+        guc->stalled_request = rq;
+        guc->submission_stall_reason = STALL_MOVE_LRC_TAIL;
      }
      return ret;
@@ -898,7 +898,7 @@ static bool multi_lrc_submit(struct i915_request *rq)
       * submitting all the requests generated in parallel.
       */
      return test_bit(I915_FENCE_FLAG_SUBMIT_PARALLEL, 
&rq->fence.flags) ||
-        intel_context_is_banned(ce);
+           !intel_context_is_schedulable(ce);
  }
  static int guc_dequeue_one_context(struct intel_guc *guc)
@@ -967,7 +967,7 @@ static int guc_dequeue_one_context(struct 
intel_guc *guc)
          struct intel_context *ce = request_to_scheduling_context(last);
          if (unlikely(!ctx_id_mapped(guc, ce->guc_id.id) &&
-                 !intel_context_is_banned(ce))) {
+                 intel_context_is_schedulable(ce))) {
              ret = try_context_registration(ce, false);
              if (unlikely(ret == -EPIPE)) {
                  goto deadlk;
@@ -1577,7 +1577,7 @@ static void guc_reset_state(struct intel_context 
*ce, u32 head, bool scrub)
  {
      struct intel_engine_cs *engine = __context_to_physical_engine(ce);
-    if (intel_context_is_banned(ce))
+    if (!intel_context_is_schedulable(ce))
          return;
      GEM_BUG_ON(!intel_context_is_pinned(ce));
@@ -4518,12 +4518,12 @@ static void guc_handle_context_reset(struct 
intel_guc *guc,
  {
      trace_intel_context_reset(ce);
-    if (likely(!intel_context_is_banned(ce))) {
+    if (likely(intel_context_is_schedulable(ce))) {
          capture_error_state(guc, ce);
          guc_context_replay(ce);
      } else {
          drm_info(&guc_to_gt(guc)->i915->drm,
-             "Ignoring context reset notification of banned context 
0x%04X on %s",
+             "Ignoring context reset notification of exiting context 
0x%04X on %s",

With small clarifications:

Reviewed-by: Andrzej Hajda <andrzej.ha...@intel.com>

Regards
Andrzej


               ce->guc_id.id, ce->engine->name);
      }
  }