drm, drm/xe: Fix xe userptr in the absence of CONFIG_DEVICE_PRIVATE

CONFIG_DEVICE_PRIVATE is not selected by default by some distros,
for example Fedora, and that leads to a regression in the xe driver
since userptr support gets compiled out.

It turns out that DRM_GPUSVM, which is needed for xe userptr support
compiles also without CONFIG_DEVICE_PRIVATE, but doesn't compile
without CONFIG_ZONE_DEVICE.
Exclude the drm_pagemap files from compilation with !CONFIG_ZONE_DEVICE,
and remove the CONFIG_DEVICE_PRIVATE dependency from CONFIG_DRM_GPUSVM and
the xe driver's selection of it, re-enabling xe userptr for those configs.

v2:
- Don't compile the drm_pagemap files unless CONFIG_ZONE_DEVICE is set.
- Adjust the drm_pagemap.h header accordingly.

Fixes: 9e9787414882 ("drm/xe/userptr: replace xe_hmm with gpusvm")
Cc: Matthew Auld <[e-mail]>
Cc: Himal Prasad Ghimiray <[e-mail]>
Cc: Thomas Hellström <[e-mail]>
Cc: Matthew Brost <[e-mail]>
Cc: "Thomas Hellström" <[e-mail]>
Cc: Rodrigo Vivi <[e-mail]>
Cc: [e-mail]
Cc: <[e-mail]> # v6.18+
Signed-off-by: Thomas Hellström <[e-mail]>
Reviewed-by: Matthew Auld <[e-mail]>
Acked-by: Maarten Lankhorst <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
(cherry picked from commit 1e372b246199ca7a35f930177fea91b557dac16e)
Signed-off-by: Thomas Hellström <[e-mail]>

drivers/gpu/drm/Kconfig

···
 
 config DRM_GPUSVM
 	tristate
-	depends on DRM && DEVICE_PRIVATE
+	depends on DRM
 	select HMM_MIRROR
 	select MMU_NOTIFIER
 	help

drivers/gpu/drm/Makefile

···
 obj-$(CONFIG_DRM_GPUVM) += drm_gpuvm.o
 
 drm_gpusvm_helper-y := \
-	drm_gpusvm.o\
+	drm_gpusvm.o
+drm_gpusvm_helper-$(CONFIG_ZONE_DEVICE) += \
 	drm_pagemap.o
+
 obj-$(CONFIG_DRM_GPUSVM) += drm_gpusvm_helper.o
 
 obj-$(CONFIG_DRM_BUDDY) += drm_buddy.o

drivers/gpu/drm/xe/Kconfig

···
 	select DRM_TTM
 	select DRM_TTM_HELPER
 	select DRM_EXEC
-	select DRM_GPUSVM if !UML && DEVICE_PRIVATE
+	select DRM_GPUSVM if !UML
 	select DRM_GPUVM
 	select DRM_SCHED
 	select MMU_NOTIFIER

include/drm/drm_pagemap.h

···
 			   struct dma_fence *pre_migrate_fence);
 };
 
+#if IS_ENABLED(CONFIG_ZONE_DEVICE)
+
+struct drm_pagemap *drm_pagemap_page_to_dpagemap(struct page *page);
+
+#else
+
+static inline struct drm_pagemap *drm_pagemap_page_to_dpagemap(struct page *page)
+{
+	return NULL;
+}
+
+#endif /* IS_ENABLED(CONFIG_ZONE_DEVICE) */
+
 /**
  * struct drm_pagemap_devmem - Structure representing a GPU SVM device memory allocation
  *
···
 	struct dma_fence *pre_migrate_fence;
 };
 
+#if IS_ENABLED(CONFIG_ZONE_DEVICE)
+
 int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
 				  struct mm_struct *mm,
 				  unsigned long start, unsigned long end,
···
 int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation);
 
 const struct dev_pagemap_ops *drm_pagemap_pagemap_ops_get(void);
-
-struct drm_pagemap *drm_pagemap_page_to_dpagemap(struct page *page);
 
 void drm_pagemap_devmem_init(struct drm_pagemap_devmem *devmem_allocation,
 			     struct device *dev, struct mm_struct *mm,
···
 			    unsigned long start, unsigned long end,
 			    struct mm_struct *mm,
 			    unsigned long timeslice_ms);
+
+#endif /* IS_ENABLED(CONFIG_ZONE_DEVICE) */
 
 #endif