drm/xe: have xe_svm_range embed one drm_gpusvm_pages

With drm_gpusvm_pages now self contained, make xe stop relying
on the drm_gpusvm_range pages and take responsibility for the page
lifecycle on the driver side.

Driver side (xe):

  - Embed struct drm_gpusvm_pages in xe_svm_range and route all
    xe accesses through it instead of range->base.pages.
  - Initialise the embedded pages via drm_gpusvm_init_pages(), which
    binds the owning &xe->drm up front, and take over the page
    lifecycle: xe_svm_range_get_pages() calls drm_gpusvm_get_pages()
    directly; the notifier event_end and xe_svm_range_free() paths
    drive unmap/free on the embedded pages object.
  - Convert the open-coded userptr pages init in xe_userptr_setup()
    to the same drm_gpusvm_init_pages() helper.
  - Switch xe_svm_range_pages_valid() to drm_gpusvm_pages_valid().

Framework side (drm_gpusvm):

  - Add a small inline drm_gpusvm_init_pages() helper that records the
    owning drm_device and initialises the per-pages state, giving
    drivers a single hook to extend.
  - Export drm_gpusvm_pages_valid() to let driver owned pages
    can query mapping state without going through a range.
  - Lifecycle change: drm_gpusvm_range_remove() no longer *triggers*
    unmap/free of the embedded pages. The unmap/free logic itself stays
    in the framework -- drm_gpusvm_free_pages() still performs the DMA
    unmap (as an idempotent backstop) and frees the dma_addr array --
    but the driver now owns *when* it runs, since the driver owns the
    drm_gpusvm_pages object.

Side effect / contract: a driver that owns a drm_gpusvm_pages is now
responsible for its lifecycle: drm_gpusvm_init_pages() before first
use, and drm_gpusvm_free_pages() when the owner goes away. Xe does the
latter from its ops->range_free callback, which the framework invokes
once the range refcount drops to zero in drm_gpusvm_range_remove().
The timely DMA unmap for the IOMMU security model still happens in the
notifier invalidate path via drm_gpusvm_unmap_pages(); the unmap inside
drm_gpusvm_free_pages() is only a backstop for pages that were never
invalidated.

Suggested-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Honglei Huang <honghuan@amd.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260630102127.392396-4-honghuan@amd.com

1 files changed, 20 insertions, 0 deletions

diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
index 842353afb27b..3f38283111cc 100644
--- a/include/drm/drm_gpusvm.h
+++ b/include/drm/drm_gpusvm.h
@@ -310,6 +310,9 @@ void drm_gpusvm_range_put(struct drm_gpusvm_range *range);
 bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
 				  struct drm_gpusvm_range *range);
 
+bool drm_gpusvm_pages_valid(struct drm_gpusvm *gpusvm,
+			    struct drm_gpusvm_pages *svm_pages);
+
 int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
 			       struct drm_gpusvm_range *range,
 			       const struct drm_gpusvm_ctx *ctx);
@@ -351,6 +354,23 @@ void drm_gpusvm_free_pages(struct drm_gpusvm *gpusvm,
 			   unsigned long npages);
 
 /**
+ * drm_gpusvm_init_pages() - Initialize a freshly allocated drm_gpusvm_pages
+ * @svm_pages: Pointer to the drm_gpusvm_pages to initialize.
+ * @drm: The DRM device that will own DMA mappings for this pages object.
+ *
+ * Drivers that embed one or more drm_gpusvm_pages in their own range
+ * structure must call this once on each pages instance after allocation,
+ * before the first drm_gpusvm_get_pages() / unmap / free.
+ */
+static inline void drm_gpusvm_init_pages(struct drm_gpusvm_pages *svm_pages,
+					 struct drm_device *drm)
+{
+	memset(svm_pages, 0, sizeof(*svm_pages));
+	svm_pages->drm = drm;
+	svm_pages->notifier_seq = LONG_MAX;
+}
+
+/**
  * enum drm_gpusvm_scan_result - Scan result from the drm_gpusvm_scan_mm() function.
  * @DRM_GPUSVM_SCAN_UNPOPULATED: At least one page was not present or inaccessible.
  * @DRM_GPUSVM_SCAN_EQUAL: All pages belong to the struct dev_pagemap indicated as