[RFC PATCH 04/19] drm/pagemap: Add a populate_mm op

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Add an operation to populate a part of a drm_mm with device
private memory.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/drm_gpusvm.c  |  7 ++-----
 drivers/gpu/drm/drm_pagemap.c | 32 ++++++++++++++++++++++++++++++++
 include/drm/drm_pagemap.h     | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 4fade7018507..d84e27283768 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -175,11 +175,8 @@
  *		}
  *
  *		if (driver_migration_policy(range)) {
- *			mmap_read_lock(mm);
- *			devmem = driver_alloc_devmem();
- *			err = drm_pagemap_migrate_to_devmem(devmem, gpusvm->mm, gpuva_start,
- *                                                          gpuva_end, driver_pgmap_owner());
- *                      mmap_read_unlock(mm);
+ *			err = drm_pagemap_populate_mm(driver_choose_drm_pagemap(),
+ *                                                    gpuva_start, gpuva_end, gpusvm->mm);
  *			if (err)	// CPU mappings may have changed
  *				goto retry;
  *		}
diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
index c46bb4384444..27e3f90cf49a 100644
--- a/drivers/gpu/drm/drm_pagemap.c
+++ b/drivers/gpu/drm/drm_pagemap.c
@@ -6,6 +6,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/migrate.h>
 #include <linux/pagemap.h>
+#include <drm/drm_drv.h>
 #include <drm/drm_pagemap.h>
 
 /**
@@ -782,3 +783,34 @@ struct drm_pagemap *drm_pagemap_page_to_dpagemap(struct page *page)
 	return zdd->devmem_allocation->dpagemap;
 }
 EXPORT_SYMBOL_GPL(drm_pagemap_page_to_dpagemap);
+
+/**
+ * drm_pagemap_populate_mm() - Populate a virtual range with device memory pages
+ * @dpagemap: Pointer to the drm_pagemap managing the device memory
+ * @start: Start of the virtual range to populate.
+ * @end: End of the virtual range to populate.
+ * @mm: Pointer to the virtual address space.
+ *
+ * Attempt to populate a virtual range with device memory pages,
+ * clearing them or migrating data from the existing pages if necessary.
+ * The function is best effort only, and implementations may vary
+ * in how hard they try to satisfy the request.
+ *
+ * Return: 0 on success, negative error code on error. If the hardware
+ * device was removed / unbound the function will return -ENODEV;
+ */
+int drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
+			    unsigned long start, unsigned long end,
+			    struct mm_struct *mm)
+{
+	int err;
+
+	if (!mmget_not_zero(mm))
+		return -EFAULT;
+	mmap_read_lock(mm);
+	err = dpagemap->ops->populate_mm(dpagemap, start, end, mm);
+	mmap_read_unlock(mm);
+	mmput(mm);
+
+	return err;
+}
diff --git a/include/drm/drm_pagemap.h b/include/drm/drm_pagemap.h
index 32f0d7f23075..c591736e7c48 100644
--- a/include/drm/drm_pagemap.h
+++ b/include/drm/drm_pagemap.h
@@ -92,6 +92,34 @@ struct drm_pagemap_ops {
 			     struct device *dev,
 			     struct drm_pagemap_device_addr addr);
 
+	/**
+	 * @populate_mm: Populate part of the mm with @dpagemap memory,
+	 * migrating existing data.
+	 * @dpagemap: The struct drm_pagemap managing the memory.
+	 * @start: The virtual start address in @mm
+	 * @end: The virtual end address in @mm
+	 * @mm: Pointer to a live mm. The caller must have an mmget()
+	 * reference.
+	 *
+	 * The caller will have the mm lock at least in read mode.
+	 * Note that there is no guarantee that the memory is resident
+	 * after the function returns, it's best effort only.
+	 * When the mm is not using the memory anymore,
+	 * it will be released. The struct drm_pagemap might have a
+	 * mechanism in place to reclaim the memory and the data will
+	 * then be migrated. Typically to system memory.
+	 * The implementation should hold sufficient runtime power-
+	 * references while pages are used in an address space and
+	 * should ideally guard against hardware device unbind in
+	 * a way such that device pages are migrated back to system
+	 * followed by device page removal. The implementation should
+	 * return -ENODEV after device removal.
+	 *
+	 * Return: 0 if successful. Negative error code on error.
+	 */
+	int (*populate_mm)(struct drm_pagemap *dpagemap,
+			   unsigned long start, unsigned long end,
+			   struct mm_struct *mm);
 };
 
 /**
@@ -202,4 +230,8 @@ void drm_pagemap_devmem_init(struct drm_pagemap_devmem *devmem_allocation,
 			     const struct drm_pagemap_devmem_ops *ops,
 			     struct drm_pagemap *dpagemap, size_t size);
 
+int drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
+			    unsigned long start, unsigned long end,
+			    struct mm_struct *mm);
+
 #endif
-- 
2.48.1