[Intel-gfx] [PATCH v2] drm/i915/gem: Don't leak non-persistent requests on changing engines

[Chris Wilson]

If we have a set of active engines marked as being non-persistent, we
lose track of those if the user replaces those engines with
I915_CONTEXT_PARAM_ENGINES. As part of our uABI contract is that
non-persistent requests are terminated if they are no longer being
tracked by the user's context (in order to prevent a lost request
causing an untracked and so unstoppable GPU hang), we need to apply the
same context cancellation upon changing engines.

Fixes: a0e047156cde ("drm/i915/gem: Make context persistence optional")
Testcase: XXX
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 52a749691a8d..20f1d3e0221f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1624,11 +1624,18 @@ set_engines(struct i915_gem_context *ctx,
 
 replace:
 	mutex_lock(&ctx->engines_mutex);
+
+	/* Flush stale requests off the old engines if required */
+	if (!i915_gem_context_is_persistent(ctx) ||
+	    !i915_modparams.enable_hangcheck)
+		kill_context(ctx);
+
 	if (args->size)
 		i915_gem_context_set_user_engines(ctx);
 	else
 		i915_gem_context_clear_user_engines(ctx);
 	set.engines = rcu_replace_pointer(ctx->engines, set.engines, 1);
+
 	mutex_unlock(&ctx->engines_mutex);
 
 	call_rcu(&set.engines->rcu, free_engines_rcu);
-- 
2.25.0