drm/xe/vm: Subclass userptr vmas

The construct allocating only parts of the vma structure when
the userptr part is not needed is very fragile. A developer could
add additional fields below the userptr part, and the code could
easily attempt to access the userptr part even if its not persent.

So introduce xe_userptr_vma which subclasses struct xe_vma the
proper way, and accordingly modify a couple of interfaces.
This should also help if adding userptr helpers to drm_gpuvm.

v2:
- Fix documentation of to_userptr_vma() (Matthew Brost)
- Fix allocation and freeing of vmas to clearer distinguish
  between the types.

Closes: https://lore.kernel.org/intel-xe/0c4cc1a7-f409-4597-b110-81f9e45d1ffe@embeddedor.com/T/#u
Fixes: a4cc60a55fd9 ("drm/xe: Only alloc userptr part of xe_vma for userptrs")
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240131091628.12318-1-thomas.hellstrom@linux.intel.com

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
index e9c907cbcd89..df4a82e960ff 100644
--- a/drivers/gpu/drm/xe/xe_vm.h
+++ b/drivers/gpu/drm/xe/xe_vm.h
@@ -160,6 +160,18 @@ static inline bool xe_vma_is_userptr(struct xe_vma *vma)
 	return xe_vma_has_no_bo(vma) && !xe_vma_is_null(vma);
 }
 
+/**
+ * to_userptr_vma() - Return a pointer to an embedding userptr vma
+ * @vma: Pointer to the embedded struct xe_vma
+ *
+ * Return: Pointer to the embedding userptr vma
+ */
+static inline struct xe_userptr_vma *to_userptr_vma(struct xe_vma *vma)
+{
+	xe_assert(xe_vma_vm(vma)->xe, xe_vma_is_userptr(vma));
+	return container_of(vma, struct xe_userptr_vma, vma);
+}
+
 u64 xe_vm_pdp4_descriptor(struct xe_vm *vm, struct xe_tile *tile);
 
 int xe_vm_create_ioctl(struct drm_device *dev, void *data,
@@ -222,9 +234,9 @@ static inline void xe_vm_reactivate_rebind(struct xe_vm *vm)
 	}
 }
 
-int xe_vma_userptr_pin_pages(struct xe_vma *vma);
+int xe_vma_userptr_pin_pages(struct xe_userptr_vma *uvma);
 
-int xe_vma_userptr_check_repin(struct xe_vma *vma);
+int xe_vma_userptr_check_repin(struct xe_userptr_vma *uvma);
 
 bool xe_vm_validate_should_retry(struct drm_exec *exec, int err, ktime_t *end);