Re: [PATCH v3 29/33] drm/xe: Add per-device dependency scheduler for IOVA defrag finalize

[Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>]

On Fri, Jul 10, 2026 at 07:56:15PM -0700, Matthew Brost wrote:
>A future patch performs the destination DMA mapping of a defrag move in
>two stages when the BO is IOVA mapped: a temporary contiguous mapping of
>just tht changed pages used for the GPU copy, followed by a post-copy
>finalize stet that tears that mapping down and links the new backing
>into the (transferred) IOVA reservation. The finalize step must run only
>after the GPU copy it depends on has completed, so it is dispatched as
>an xe_dep_job,

Assisted-by: LLM

NIT...minor types 'tht', 'stet' and trailing comma.

>
>Add a per-device xe_dep_scheduler dedicated to these finalize jobs,
>created in xe_bo_defrag_init() (after the migrate contexts are up) and
>torn down in xe_bo_defrag_fini(). No users yet; the job itself is added
>in a later patch.
>
>Cc: Carlos Santa <carlos.santa@intel.com>
>Cc: Ryan Neph <ryanneph@google.com>
>Cc: Christian Koenig <christian.koenig@amd.com>
>Cc: Huang Rui <ray.huang@amd.com>
>Cc: Matthew Auld <matthew.auld@intel.com>
>Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>Cc: Maxime Ripard <mripard@kernel.org>
>Cc: Thomas Zimmermann <tzimmermann@suse.de>
>Cc: David Airlie <airlied@gmail.com>
>Cc: Simona Vetter <simona@ffwll.ch>
>Cc: dri-devel@lists.freedesktop.org
>Cc: linux-kernel@vger.kernel.org
>Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>Assisted-by: GitHub_Copilot:claude-opus-4.8
>Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>---
> drivers/gpu/drm/xe/xe_bo.c           | 15 +++++++++++++++
> drivers/gpu/drm/xe/xe_device_types.h | 10 ++++++++++
> 2 files changed, 25 insertions(+)
>
>diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
>index d54e69aefeba..c5022c16411f 100644
>--- a/drivers/gpu/drm/xe/xe_bo.c
>+++ b/drivers/gpu/drm/xe/xe_bo.c
>@@ -25,6 +25,7 @@
> #include <trace/events/gpu_mem.h>
>
> #include "xe_device.h"
>+#include "xe_dep_scheduler.h"
> #include "xe_dma_buf.h"
> #include "xe_drm_client.h"
> #include "xe_ggtt.h"
>@@ -1306,6 +1307,10 @@ static void xe_bo_defrag_fini(void *arg)
> 	struct xe_device *xe = arg;
>
> 	disable_delayed_work_sync(&xe->mem.defrag.worker);
>+	if (xe->mem.defrag.iova_sched) {
>+		xe_dep_scheduler_fini(xe->mem.defrag.iova_sched);

LLM suggests adding drm_sched_entity_flush() after calling
disable_delayed_work_sync() but before calling xe_dep_scheduler_fini().

>+		xe->mem.defrag.iova_sched = NULL;
>+	}
> }
>
> /**
>@@ -1342,6 +1347,16 @@ void xe_bo_defrag_init_early(struct xe_device *xe)
>  */
> int xe_bo_defrag_init(struct xe_device *xe)
> {
>+#define XE_BO_MAX_IOVA_DEFRAG_JOBS	16	/* Picking a reasonable value */
>+	struct xe_dep_scheduler *iova_sched;
>+
>+	iova_sched = xe_dep_scheduler_create(xe, NULL, "xe_iova_defrag",
>+					     XE_BO_MAX_IOVA_DEFRAG_JOBS);

Should we be creating this only if IOMMU is enabled (IOVA supported)
and defragmentation is enabled?

>+	if (IS_ERR(iova_sched))
>+		return PTR_ERR(iova_sched);

returning early here skips registering xe_bo_defrag_fini. Though it is
unlikely that defrag worker getting scheduled by this time, it is
probably still good to register xe_bo_defrag_fini to ensure worker
is stopped.

Niranjana

>+	xe->mem.defrag.iova_sched = iova_sched;
>+#undef XE_BO_MAX_IOVA_DEFRAG_JOBS
>+
> 	return devm_add_action_or_reset(xe->drm.dev, xe_bo_defrag_fini, xe);
> }
>
>diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
>index 6e68add4d652..b55d549d5e30 100644
>--- a/drivers/gpu/drm/xe/xe_device_types.h
>+++ b/drivers/gpu/drm/xe/xe_device_types.h
>@@ -38,6 +38,7 @@
>
> struct drm_pagemap_shrinker;
> struct intel_display;
>+struct xe_dep_scheduler;
> struct intel_dg_nvm_dev;
> struct xe_ggtt;
> struct xe_i2c;
>@@ -325,6 +326,15 @@ struct xe_device {
> 			 * @mem.defrag.worker, in milliseconds.
> 			 */
> 			unsigned int interval_ms;
>+			/**
>+			 * @mem.defrag.iova_sched: Dependency scheduler used to
>+			 * run the post-copy IOVA finalize job for defrag moves
>+			 * of IOVA-mapped BOs. The job tears down the temporary
>+			 * copy-step IOVA mapping and links the new backing into
>+			 * the (transferred) reservation once the GPU copy that
>+			 * its dependencies gate has completed.
>+			 */
>+			struct xe_dep_scheduler *iova_sched;
> 		} defrag;
> 	} mem;
>
>-- 
>2.34.1
>