Commit ec172c7b authored by Tomasz Lis's avatar Tomasz Lis Committed by Michal Wajdeczko
Browse files

drm/xe: Wrappers for setting and getting LRC references 



There is a small but non-zero chance that VF post migration fixups
are running on an exec queue during teardown. The chances are
decreased by starting the teardown by releasing guc_id, but remain
non-zero. On the other hand the sync between fixups and EQ creation
(wait_valid_ggtt) drastically increases the chance for such parallel
teardown if queue creation error path is entered (err_lrc label).

The exec queue itself is not going to cause an issue, but LRCs have
a small chance of getting freed during the fixups.

Creating a setter and a getter makes it easier to protect the fixup
operations with a lock. For other driver activities, the original
access method (without any protection) can still be used.

v2: Separate lock, only for LRCs. Kerneldoc fixes. Subject tag fix.

Signed-off-by: default avatarTomasz Lis <tomasz.lis@intel.com>
Reviewed-by: default avatarMatthew Brost <matthew.brost@intel.com>
Signed-off-by: default avatarMichal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patch.msgid.link/20260226212701.2937065-3-tomasz.lis@intel.com
parent 393e5fea

drivers/gpu/drm/xe/xe_exec_queue.c

+54 −19
Original line number Diff line number Diff line
@@ -231,6 +231,7 @@ static struct xe_exec_queue *__xe_exec_queue_alloc(struct xe_device *xe, 
	INIT_LIST_HEAD(&q->hw_engine_group_link);

	INIT_LIST_HEAD(&q->pxp.link);

	spin_lock_init(&q->multi_queue.lock);

	spin_lock_init(&q->lrc_lookup_lock);

	q->multi_queue.priority = XE_MULTI_QUEUE_PRIORITY_NORMAL;



	q->sched_props.timeslice_us = hwe->eclass->sched_props.timeslice_us;
@@ -270,6 +271,56 @@ static struct xe_exec_queue *__xe_exec_queue_alloc(struct xe_device *xe, 
	return q;

}



static void xe_exec_queue_set_lrc(struct xe_exec_queue *q, struct xe_lrc *lrc, u16 idx)

{

	xe_assert(gt_to_xe(q->gt), idx < q->width);



	scoped_guard(spinlock, &q->lrc_lookup_lock)

		q->lrc[idx] = lrc;

}



/**

 * xe_exec_queue_get_lrc() - Get the LRC from exec queue.

 * @q: The exec queue instance.

 * @idx: Index within multi-LRC array.

 *

 * Retrieves LRC of given index for the exec queue under lock

 * and takes reference.

 *

 * Return: Pointer to LRC on success, error on failure, NULL on

 * lookup failure.

 */

struct xe_lrc *xe_exec_queue_get_lrc(struct xe_exec_queue *q, u16 idx)

{

	struct xe_lrc *lrc;



	xe_assert(gt_to_xe(q->gt), idx < q->width);



	scoped_guard(spinlock, &q->lrc_lookup_lock) {

		lrc = q->lrc[idx];

		if (lrc)

			xe_lrc_get(lrc);

	}



	return lrc;

}



/**

 * xe_exec_queue_lrc() - Get the LRC from exec queue.

 * @q: The exec queue instance.

 *

 * Retrieves the primary LRC for the exec queue. Note that this function

 * returns only the first LRC instance, even when multiple parallel LRCs

 * are configured. This function does not increment reference count,

 * so the reference can be just forgotten after use.

 *

 * Return: Pointer to LRC on success, error on failure

 */

struct xe_lrc *xe_exec_queue_lrc(struct xe_exec_queue *q)

{

	return q->lrc[0];

}



static void __xe_exec_queue_fini(struct xe_exec_queue *q)

{

	int i;
@@ -327,8 +378,7 @@ static int __xe_exec_queue_init(struct xe_exec_queue *q, u32 exec_queue_flags) 
			goto err_lrc;

		}



		/* Pairs with READ_ONCE to xe_exec_queue_contexts_hwsp_rebase */

		WRITE_ONCE(q->lrc[i], lrc);

		xe_exec_queue_set_lrc(q, lrc, i);

	}



	return 0;
@@ -1293,21 +1343,6 @@ int xe_exec_queue_get_property_ioctl(struct drm_device *dev, void *data, 
	return ret;

}



/**

 * xe_exec_queue_lrc() - Get the LRC from exec queue.

 * @q: The exec_queue.

 *

 * Retrieves the primary LRC for the exec queue. Note that this function

 * returns only the first LRC instance, even when multiple parallel LRCs

 * are configured.

 *

 * Return: Pointer to LRC on success, error on failure

 */

struct xe_lrc *xe_exec_queue_lrc(struct xe_exec_queue *q)

{

	return q->lrc[0];

}



/**

 * xe_exec_queue_is_lr() - Whether an exec_queue is long-running

 * @q: The exec_queue
@@ -1667,14 +1702,14 @@ int xe_exec_queue_contexts_hwsp_rebase(struct xe_exec_queue *q, void *scratch) 
	for (i = 0; i < q->width; ++i) {

		struct xe_lrc *lrc;



		/* Pairs with WRITE_ONCE in __xe_exec_queue_init  */

		lrc = READ_ONCE(q->lrc[i]);

		lrc = xe_exec_queue_get_lrc(q, i);

		if (!lrc)

			continue;



		xe_lrc_update_memirq_regs_with_address(lrc, q->hwe, scratch);

		xe_lrc_update_hwctx_regs_with_address(lrc);

		err = xe_lrc_setup_wa_bb_with_scratch(lrc, q->hwe, scratch);

		xe_lrc_put(lrc);

		if (err)

			break;

	}

drivers/gpu/drm/xe/xe_exec_queue.h

+1 −0
Original line number Diff line number Diff line
@@ -160,6 +160,7 @@ void xe_exec_queue_update_run_ticks(struct xe_exec_queue *q); 
int xe_exec_queue_contexts_hwsp_rebase(struct xe_exec_queue *q, void *scratch);



struct xe_lrc *xe_exec_queue_lrc(struct xe_exec_queue *q);

struct xe_lrc *xe_exec_queue_get_lrc(struct xe_exec_queue *q, u16 idx);



/**

 * xe_exec_queue_idle_skip_suspend() - Can exec queue skip suspend

drivers/gpu/drm/xe/xe_exec_queue_types.h

+5 −0
Original line number Diff line number Diff line
@@ -257,6 +257,11 @@ struct xe_exec_queue { 
	u64 tlb_flush_seqno;

	/** @hw_engine_group_link: link into exec queues in the same hw engine group */

	struct list_head hw_engine_group_link;

	/**

	 * @lrc_lookup_lock: Lock for protecting lrc array access. Only used when

	 * running in parallel to queue creation is possible.

	 */

	spinlock_t lrc_lookup_lock;

	/** @lrc: logical ring context for this exec queue */

	struct xe_lrc *lrc[] __counted_by(width);

};