[PATCH v4 12/17] drm/i915/pxp: start the arb session on demand

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

Now that we can handle destruction and re-creation of the arb session,
we can postpone the start of the session to the first submission that
requires it, to avoid keeping it running with no user.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
---
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    |  8 ++--
 drivers/gpu/drm/i915/pxp/intel_pxp.c          | 37 ++++++++++++-------
 drivers/gpu/drm/i915/pxp/intel_pxp.h          |  4 +-
 drivers/gpu/drm/i915/pxp/intel_pxp_irq.c      |  2 +-
 drivers/gpu/drm/i915/pxp/intel_pxp_session.c  |  6 +--
 drivers/gpu/drm/i915/pxp/intel_pxp_tee.c      | 10 +----
 drivers/gpu/drm/i915/pxp/intel_pxp_types.h    |  3 ++
 7 files changed, 39 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index a11e9d5767bf..c08e28847064 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2948,9 +2948,11 @@ eb_select_engine(struct i915_execbuffer *eb)
 	intel_gt_pm_get(ce->engine->gt);
 
 	if (i915_gem_context_uses_protected_content(eb->gem_context)) {
-		err = intel_pxp_wait_for_arb_start(&ce->engine->gt->pxp);
-		if (err)
-			goto err;
+		if (!intel_pxp_is_active(&ce->engine->gt->pxp)) {
+			err = intel_pxp_start(&ce->engine->gt->pxp);
+			if (err)
+				goto err;
+		}
 
 		if (i915_gem_context_invalidated(eb->gem_context)) {
 			err = -EACCES;
diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.c b/drivers/gpu/drm/i915/pxp/intel_pxp.c
index f713d3423cea..2291c68fd3a0 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp.c
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp.c
@@ -77,6 +77,7 @@ void intel_pxp_init(struct intel_pxp *pxp)
 	init_completion(&pxp->termination);
 	complete_all(&pxp->termination);
 
+	mutex_init(&pxp->arb_mutex);
 	INIT_WORK(&pxp->session_work, intel_pxp_session_work);
 
 	ret = create_vcs_context(pxp);
@@ -113,7 +114,7 @@ void intel_pxp_mark_termination_in_progress(struct intel_pxp *pxp)
 	reinit_completion(&pxp->termination);
 }
 
-static void intel_pxp_queue_termination(struct intel_pxp *pxp)
+static void pxp_queue_termination(struct intel_pxp *pxp)
 {
 	struct intel_gt *gt = pxp_to_gt(pxp);
 
@@ -132,31 +133,41 @@ static void intel_pxp_queue_termination(struct intel_pxp *pxp)
  * the arb session is restarted from the irq work when we receive the
  * termination completion interrupt
  */
-int intel_pxp_wait_for_arb_start(struct intel_pxp *pxp)
+int intel_pxp_start(struct intel_pxp *pxp)
 {
+	int ret = 0;
+
 	if (!intel_pxp_is_enabled(pxp))
-		return 0;
+		return -ENODEV;
+
+	mutex_lock(&pxp->arb_mutex);
+
+	if (pxp->arb_is_valid)
+		goto unlock;
+
+	pxp_queue_termination(pxp);
 
 	if (!wait_for_completion_timeout(&pxp->termination,
-					 msecs_to_jiffies(100)))
-		return -ETIMEDOUT;
+					msecs_to_jiffies(100))) {
+		ret = -ETIMEDOUT;
+		goto unlock;
+	}
+
+	/* make sure the compiler doesn't optimize the double access */
+	barrier();
 
 	if (!pxp->arb_is_valid)
-		return -EIO;
+		ret = -EIO;
 
-	return 0;
+unlock:
+	mutex_unlock(&pxp->arb_mutex);
+	return ret;
 }
 
 void intel_pxp_init_hw(struct intel_pxp *pxp)
 {
 	kcr_pxp_enable(pxp_to_gt(pxp));
 	intel_pxp_irq_enable(pxp);
-
-	/*
-	 * the session could've been attacked while we weren't loaded, so
-	 * handle it as if it was and re-create it.
-	 */
-	intel_pxp_queue_termination(pxp);
 }
 
 void intel_pxp_fini_hw(struct intel_pxp *pxp)
diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.h b/drivers/gpu/drm/i915/pxp/intel_pxp.h
index 91c1a2056309..1f9871e64096 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp.h
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp.h
@@ -32,7 +32,7 @@ void intel_pxp_init_hw(struct intel_pxp *pxp);
 void intel_pxp_fini_hw(struct intel_pxp *pxp);
 
 void intel_pxp_mark_termination_in_progress(struct intel_pxp *pxp);
-int intel_pxp_wait_for_arb_start(struct intel_pxp *pxp);
+int intel_pxp_start(struct intel_pxp *pxp);
 void intel_pxp_invalidate(struct intel_pxp *pxp);
 #else
 static inline void intel_pxp_init(struct intel_pxp *pxp)
@@ -43,7 +43,7 @@ static inline void intel_pxp_fini(struct intel_pxp *pxp)
 {
 }
 
-static inline int intel_pxp_wait_for_arb_start(struct intel_pxp *pxp)
+static inline int intel_pxp_start(struct intel_pxp *pxp)
 {
 	return 0;
 }
diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c b/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c
index 196449243515..a230d0034e50 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp_irq.c
@@ -31,7 +31,7 @@ void intel_pxp_irq_handler(struct intel_pxp *pxp, u16 iir)
 		   GEN12_DISPLAY_APP_TERMINATED_PER_FW_REQ_INTERRUPT)) {
 		/* immediately mark PXP as inactive on termination */
 		intel_pxp_mark_termination_in_progress(pxp);
-		pxp->session_events |= PXP_TERMINATION_REQUEST;
+		pxp->session_events |= PXP_TERMINATION_REQUEST | PXP_INVAL_REQUIRED;
 	}
 
 	if (iir & GEN12_DISPLAY_STATE_RESET_COMPLETE_INTERRUPT)
diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_session.c b/drivers/gpu/drm/i915/pxp/intel_pxp_session.c
index e9fe757e368a..c21620916710 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp_session.c
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp_session.c
@@ -85,9 +85,6 @@ static int pxp_terminate_arb_session_and_global(struct intel_pxp *pxp)
 	/* must mark termination in progress calling this function */
 	GEM_WARN_ON(pxp->arb_is_valid);
 
-	/* invalidate protected objects */
-	intel_pxp_invalidate(pxp);
-
 	/* terminate the hw sessions */
 	ret = intel_pxp_terminate_session(pxp, ARB_SESSION);
 	if (ret) {
@@ -144,6 +141,9 @@ void intel_pxp_session_work(struct work_struct *work)
 	if (!events)
 		return;
 
+	if (events & PXP_INVAL_REQUIRED)
+		intel_pxp_invalidate(pxp);
+
 	if (events & PXP_TERMINATION_REQUEST) {
 		events &= ~PXP_TERMINATION_COMPLETE;
 		pxp_terminate(pxp);
diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c b/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
index e3d178c44e51..35b3fed4ca2f 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
@@ -63,23 +63,15 @@ static int intel_pxp_tee_io_message(struct intel_pxp *pxp,
 static int i915_pxp_tee_component_bind(struct device *i915_kdev,
 				       struct device *tee_kdev, void *data)
 {
-	struct drm_i915_private *i915 = kdev_to_i915(i915_kdev);
 	struct intel_pxp *pxp = i915_dev_to_pxp(i915_kdev);
-	int ret;
 
 	pxp->pxp_component = data;
 	pxp->pxp_component->tee_dev = tee_kdev;
 
 	/* the component is required to fully start the PXP HW */
 	intel_pxp_init_hw(pxp);
-	ret = intel_pxp_wait_for_arb_start(pxp);
-	if (ret) {
-		drm_err(&i915->drm, "Failed to create arb session during bind\n");
-		intel_pxp_fini_hw(pxp);
-		pxp->pxp_component = NULL;
-	}
 
-	return ret;
+	return 0;
 }
 
 static void i915_pxp_tee_component_unbind(struct device *i915_kdev,
diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_types.h b/drivers/gpu/drm/i915/pxp/intel_pxp_types.h
index c059a17cbcfe..b3ae49dd73a8 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp_types.h
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp_types.h
@@ -7,6 +7,7 @@
 #define __INTEL_PXP_TYPES_H__
 
 #include <linux/completion.h>
+#include <linux/mutex.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 
@@ -23,6 +24,7 @@ struct intel_pxp {
 	 * even if the keys are gone, so we can't rely on the HW state of the
 	 * session to know if it's valid and need to track the status in SW.
 	 */
+	struct mutex arb_mutex; /* protects arb session start */
 	bool arb_is_valid;
 
 	/*
@@ -40,6 +42,7 @@ struct intel_pxp {
 	u32 session_events; /* protected with gt->irq_lock */
 #define PXP_TERMINATION_REQUEST  BIT(0)
 #define PXP_TERMINATION_COMPLETE BIT(1)
+#define PXP_INVAL_REQUIRED       BIT(2)
 };
 
 #endif /* __INTEL_PXP_TYPES_H__ */
-- 
2.29.2