drm/pagemap, drm/xe: Add refcounting to struct drm_pagemap

With the end goal of being able to free unused pagemaps
and allocate them on demand, add a refcount to struct drm_pagemap,
remove the xe embedded drm_pagemap, allocating and freeing it
explicitly.

v2:
- Make the drm_pagemap pointer in drm_gpusvm_pages reference-counted.
v3:
- Call drm_pagemap_get() before drm_pagemap_put() in drm_gpusvm_pages
  (Himal Prasad Ghimiray)

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com> #v1
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe.
Link: https://patch.msgid.link/20251219113320.183860-5-thomas.hellstrom@linux.intel.com

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 39c8c50401dd068d5be43c049997168630744201..4c7474a331bc3cb348ded563002e67f211e027b9 100644 (file)
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -1038,6 +1038,7 @@ static void __drm_gpusvm_unmap_pages(struct drm_gpusvm *gpusvm,
                flags.has_dma_mapping = false;
                WRITE_ONCE(svm_pages->flags.__flags, flags.__flags);
 
+               drm_pagemap_put(svm_pages->dpagemap);
                svm_pages->dpagemap = NULL;
        }
 }
@@ -1434,6 +1435,8 @@ map_pages:
 
        if (pagemap) {
                flags.has_devmem_pages = true;
+               drm_pagemap_get(dpagemap);
+               drm_pagemap_put(svm_pages->dpagemap);
                svm_pages->dpagemap = dpagemap;
        }
 

diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
index ac3832f851903f3a88819e045fa821c05d91a3da..87648a498a31d9e86da24d9fc75e7d9acbe33563 100644 (file)
--- a/drivers/gpu/drm/drm_pagemap.c
+++ b/drivers/gpu/drm/drm_pagemap.c
@@ -543,6 +543,57 @@ next_put:
        return -ENOMEM;
 }
 
+static void drm_pagemap_release(struct kref *ref)
+{
+       struct drm_pagemap *dpagemap = container_of(ref, typeof(*dpagemap), ref);
+
+       kfree(dpagemap);
+}
+
+/**
+ * drm_pagemap_create() - Create a struct drm_pagemap.
+ * @dev: Pointer to a struct device providing the device-private memory.
+ * @pagemap: Pointer to a pre-setup struct dev_pagemap providing the struct pages.
+ * @ops: Pointer to the struct drm_pagemap_ops.
+ *
+ * Allocate and initialize a struct drm_pagemap.
+ *
+ * Return: A refcounted pointer to a struct drm_pagemap on success.
+ * Error pointer on error.
+ */
+struct drm_pagemap *
+drm_pagemap_create(struct device *dev,
+                  struct dev_pagemap *pagemap,
+                  const struct drm_pagemap_ops *ops)
+{
+       struct drm_pagemap *dpagemap = kzalloc(sizeof(*dpagemap), GFP_KERNEL);
+
+       if (!dpagemap)
+               return ERR_PTR(-ENOMEM);
+
+       kref_init(&dpagemap->ref);
+       dpagemap->dev = dev;
+       dpagemap->ops = ops;
+       dpagemap->pagemap = pagemap;
+
+       return dpagemap;
+}
+EXPORT_SYMBOL(drm_pagemap_create);
+
+/**
+ * drm_pagemap_put() - Put a struct drm_pagemap reference
+ * @dpagemap: Pointer to a struct drm_pagemap object.
+ *
+ * Puts a struct drm_pagemap reference and frees the drm_pagemap object
+ * if the refount reaches zero.
+ */
+void drm_pagemap_put(struct drm_pagemap *dpagemap)
+{
+       if (likely(dpagemap))
+               kref_put(&dpagemap->ref, drm_pagemap_release);
+}
+EXPORT_SYMBOL(drm_pagemap_put);
+
 /**
  * drm_pagemap_evict_to_ram() - Evict GPU SVM range to RAM
  * @devmem_allocation: Pointer to the device memory allocation

diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index 14a027b3ee6b00a52b2d880e82ad330a9aacadf0..b30daedb9a5f9cb87cbc137ceeed59b18eebd796 100644 (file)
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -868,7 +868,7 @@ static int xe_drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
                                      struct mm_struct *mm,
                                      unsigned long timeslice_ms)
 {
-       struct xe_vram_region *vr = container_of(dpagemap, typeof(*vr), dpagemap);
+       struct xe_vram_region *vr = container_of(dpagemap->pagemap, typeof(*vr), pagemap);
        struct dma_fence *pre_migrate_fence = NULL;
        struct xe_device *xe = vr->xe;
        struct device *dev = xe->drm.dev;
@@ -1392,7 +1392,7 @@ u8 xe_svm_ranges_zap_ptes_in_range(struct xe_vm *vm, u64 start, u64 end)
 
 static struct drm_pagemap *tile_local_pagemap(struct xe_tile *tile)
 {
-       return &tile->mem.vram->dpagemap;
+       return tile->mem.vram->dpagemap;
 }
 
 /**
@@ -1502,6 +1502,15 @@ int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr)
                return ret;
        }
 
+       vr->dpagemap = drm_pagemap_create(dev, &vr->pagemap,
+                                         &xe_drm_pagemap_ops);
+       if (IS_ERR(vr->dpagemap)) {
+               drm_err(&xe->drm, "Failed to create drm_pagemap tile %d memory: %pe\n",
+                       tile->id, vr->dpagemap);
+               ret = PTR_ERR(vr->dpagemap);
+               goto out_no_dpagemap;
+       }
+
        vr->pagemap.type = MEMORY_DEVICE_PRIVATE;
        vr->pagemap.range.start = res->start;
        vr->pagemap.range.end = res->end;
@@ -1509,22 +1518,23 @@ int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr)
        vr->pagemap.ops = drm_pagemap_pagemap_ops_get();
        vr->pagemap.owner = xe_svm_devm_owner(xe);
        addr = devm_memremap_pages(dev, &vr->pagemap);
-
-       vr->dpagemap.dev = dev;
-       vr->dpagemap.ops = &xe_drm_pagemap_ops;
-
        if (IS_ERR(addr)) {
-               devm_release_mem_region(dev, res->start, resource_size(res));
                ret = PTR_ERR(addr);
                drm_err(&xe->drm, "Failed to remap tile %d memory, errno %pe\n",
                        tile->id, ERR_PTR(ret));
-               return ret;
+               goto out_failed_memremap;
        }
        vr->hpa_base = res->start;
 
        drm_dbg(&xe->drm, "Added tile %d memory [%llx-%llx] to devm, remapped to %pr\n",
                tile->id, vr->io_start, vr->io_start + vr->usable_size, res);
        return 0;
+
+out_failed_memremap:
+       drm_pagemap_put(vr->dpagemap);
+out_no_dpagemap:
+       devm_release_mem_region(dev, res->start, resource_size(res));
+       return ret;
 }
 #else
 int xe_svm_alloc_vram(struct xe_tile *tile,

diff --git a/drivers/gpu/drm/xe/xe_vram_types.h b/drivers/gpu/drm/xe/xe_vram_types.h
index 83772dcbf1aff97db85b429c295b8e51d7e003db..c0d2c5ee8c104427666ea7f191254f6b90dbed63 100644 (file)
--- a/drivers/gpu/drm/xe/xe_vram_types.h
+++ b/drivers/gpu/drm/xe/xe_vram_types.h
@@ -72,7 +72,7 @@ struct xe_vram_region {
         * @dpagemap: The struct drm_pagemap of the ZONE_DEVICE memory
         * pages of this tile.
         */
-       struct drm_pagemap dpagemap;
+       struct drm_pagemap *dpagemap;
        /**
         * @hpa_base: base host physical address
         *

diff --git a/include/drm/drm_pagemap.h b/include/drm/drm_pagemap.h
index 70a7991f784f9b06afddd74238c0bb8274d94337..093e7199c44b7df389a236911ec3055b100f357f 100644 (file)
--- a/include/drm/drm_pagemap.h
+++ b/include/drm/drm_pagemap.h
@@ -130,11 +130,15 @@ struct drm_pagemap_ops {
  * struct drm_pagemap: Additional information for a struct dev_pagemap
  * used for device p2p handshaking.
  * @ops: The struct drm_pagemap_ops.
+ * @ref: Reference count.
  * @dev: The struct drevice owning the device-private memory.
+ * @pagemap: Pointer to the underlying dev_pagemap.
  */
 struct drm_pagemap {
        const struct drm_pagemap_ops *ops;
+       struct kref ref;
        struct device *dev;
+       struct dev_pagemap *pagemap;
 };
 
 struct drm_pagemap_devmem;
@@ -209,6 +213,37 @@ struct drm_pagemap_devmem_ops {
                           struct dma_fence *pre_migrate_fence);
 };
 
+struct drm_pagemap *drm_pagemap_create(struct device *dev,
+                                      struct dev_pagemap *pagemap,
+                                      const struct drm_pagemap_ops *ops);
+
+#if IS_ENABLED(CONFIG_DRM_GPUSVM)
+
+void drm_pagemap_put(struct drm_pagemap *dpagemap);
+
+#else
+
+static inline void drm_pagemap_put(struct drm_pagemap *dpagemap)
+{
+}
+
+#endif /* IS_ENABLED(CONFIG_DRM_GPUSVM) */
+
+/**
+ * drm_pagemap_get() - Obtain a reference on a struct drm_pagemap
+ * @dpagemap: Pointer to the struct drm_pagemap.
+ *
+ * Return: Pointer to the struct drm_pagemap.
+ */
+static inline struct drm_pagemap *
+drm_pagemap_get(struct drm_pagemap *dpagemap)
+{
+       if (likely(dpagemap))
+               kref_get(&dpagemap->ref);
+
+       return dpagemap;
+}
+
 /**
  * struct drm_pagemap_devmem - Structure representing a GPU SVM device memory allocation
  *
@@ -257,3 +292,4 @@ int drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
                            unsigned long timeslice_ms);
 
 #endif
+