[CI 09/42] drm/svm: introduce drm_mem_region concept

[Oak Zeng]

As its name indicates, a drm_mem_region represent a memory region on
a drm device, e.g., a GPU's HBM memory.

In a memory region, we have address information of this region, from
both CPU (hpa_base) and GPU (dpa_base) perspectives. It has a pagemap
member which is used to memremap memory region to ZONE_DEVICE. It also
has some interfaces for drm to callback driver to allocate/free memory from
this region, migrate data to/from this memory region, get a pagemap
owner of a memory region, and get the drm device which own the memory
region.

This is introduced for system allocator implementation, so the memory
allocation and free interfaces are page based.

A few helper functions are also introduced:
1) drm_mem_region_page_to_dpa: calculate device physical address for
   a page
2) drm_page_to_mem_region: retrieve drm memory region that a page
   resides in

v1: use page parameter instead of pfn (Matt)
Add BUG_ON(mr != drm_page_to_mem_region(page)) (Matt)

Cc: Dave Airlie <airlied at redhat.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Felix Kuehling <felix.kuehling at amd.com>
Cc: Jason Gunthorpe <jgg at nvidia.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Brian Welty <brian.welty at intel.com>
Cc: <dri-devel at lists.freedesktop.org>
Signed-off-by: Oak Zeng <oak.zeng at intel.com>
---
 include/drm/drm_svm.h | 162 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 include/drm/drm_svm.h

diff --git a/include/drm/drm_svm.h b/include/drm/drm_svm.h
new file mode 100644
index 000000000000..a383c7251e2b
--- /dev/null
+++ b/include/drm/drm_svm.h
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _DRM_SVM__
+#define _DRM_SVM__
+
+#include <linux/compiler_types.h>
+#include <linux/memremap.h>
+#include <linux/types.h>
+
+struct dma_fence;
+struct drm_mem_region;
+
+/**
+ * struct migrate_vec - a migration vector is an array of addresses,
+ * each of which represents one page.
+ * When it is system memory page, the address is a dmap-mapped address.
+ * When it is vram page, the address is device physical address.
+ */
+struct migrate_vec {
+	/**
+	 * @mr: the memory region that pages reside.
+	 * When it is system memory page, mr is NULL.
+	 */
+	struct drm_mem_region *mr;
+	/** @npages: number of pages */
+	u64 npages;
+	/**
+	 * @addr_vec: address vector
+	 * each item in addr_vec is an address of a page
+	 */
+	union {
+		/** @dma_addr: dma-mapped address of the page, only valid for system pages*/
+		dma_addr_t dma_addr;
+		/** @dpa: device physical address of the page, only valid for vram page*/
+		phys_addr_t dpa;
+	} addr_vec[1];
+};
+
+/**
+ * struct drm_mem_region_ops - memory region operations such as memory allocation
+ * and migration etc. Driver is supposed to implement those operations.
+ */
+struct drm_mem_region_ops {
+	/**
+	 * @drm_mem_region_alloc_pages: Called from drm to driver to allocate
+	 * device VRAM memory
+	 * @mr: The memory region where to allocate device VRAM memory from
+	 * @npages: number of pages to allocate
+	 * @pfns: Used to return pfns of each page
+	 */
+	int (*drm_mem_region_alloc_pages) (struct drm_mem_region *mr,
+						unsigned long npags, unsigned long *pfns);
+	/**
+	 * @drm_mem_region_free_page: Called from drm to free one page of device memory
+	 * @page: point to the page to free
+	 */
+	void (*drm_mem_region_free_page) (struct page *page);
+	/**
+	 * @drm_mem_region_migrate: Called from drm to migrate memory from src to
+	 * dst. Driver is supposed to implement this function using device hardware
+	 * accelerators such as DMA. DRM subsystem call this function to migrate
+	 * memory b/t system memory and device memory region
+	 *
+	 * @src_vec: source migration vector
+	 * @dst_vec: destination migration vector
+	 */
+	struct dma_fence* (*drm_mem_region_migrate)(struct migrate_vec *src_vec,
+			struct migrate_vec *dst_vec);
+	/**
+	 * @drm_mem_region_pagemap_owner: Return the pagemap owner of a memory
+	 * region. Pagemap owner is the owner of the device memory. It is
+	 * defined by device driver and opaque to drm layer. Drm uses pagemap
+	 * owner to set up page migrations (see hmm function migrate_vma_setup)
+	 * and range population (see hmm functio hmm_range_fault). Driver has
+	 * the freedom to choose the right pagemap owner.
+	 *
+	 * @mr: the memory region which we want to get the page map owner
+	 */
+	void* (*drm_mem_region_pagemap_owner)(struct drm_mem_region *mr);
+	/**
+	 * @drm_mem_region_get_device: Return the drm device which has this memory
+	 * region.
+	 *
+	 * @mr: the memory region
+	 */
+	struct drm_device* (*drm_mem_region_get_device)(struct drm_mem_region *mr);
+};
+
+/**
+ * struct drm_mem_region - memory region structure
+ * This is used to describe a memory region in drm
+ * device, such as HBM memory or CXL extension memory.
+ *
+ * drm_mem_region is converted from the xe_mem_region
+ * concept. xe_mem_region is moved to drm layer and renamed
+ * as drm_mem_region.
+ *
+ * drm_mem_region is supposed to be embedded in some driver struct such as
+ * "struct xe_tile" or "struct amdgpu_device"
+ */
+struct drm_mem_region {
+	/** @dev_private: device private data which is opaque to drm layer */
+	void *dev_private;
+	/** @dpa_base: This memory regions's DPA (device physical address) base */
+	resource_size_t dpa_base;
+	/**
+	 * @usable_size: usable size of VRAM
+	 *
+	 * Usable size of VRAM excluding reserved portions
+	 * (e.g stolen mem)
+	 */
+	resource_size_t usable_size;
+	/** @pagemap: Used to remap device memory as ZONE_DEVICE */
+	struct dev_pagemap pagemap;
+	/**
+	 * @hpa_base: base host physical address
+	 *
+	 * This is generated when remap device memory as ZONE_DEVICE
+	 */
+	resource_size_t hpa_base;
+	/**
+	 * @mr_ops: memory region operation function pointers
+	 */
+	struct drm_mem_region_ops mr_ops;
+};
+
+/**
+ * drm_page_to_mem_region() - Get a page's memory region
+ *
+ * @page: a struct page pointer pointing to a page in vram memory region
+ */
+static inline struct drm_mem_region *drm_page_to_mem_region(struct page *page)
+{
+	return container_of(page->pgmap, struct drm_mem_region, pagemap);
+}
+
+/**
+ * drm_mem_region_page_to_dpa() - Calculate page's device physical address
+ *
+ * @mr: The memory region that page resides in
+ * @page: page to calculate dpa for
+ *
+ * Returns: the device physical address of the page
+ */
+static inline u64 drm_mem_region_page_to_dpa(struct drm_mem_region *mr, struct page *page)
+{
+	u64 pfn = page_to_pfn(page);
+	u64 offset;
+	u64 dpa;
+
+	BUG_ON(mr != drm_page_to_mem_region(page));
+	BUG_ON((pfn << PAGE_SHIFT) < mr->hpa_base );
+	BUG_ON((pfn << PAGE_SHIFT) >=  mr->hpa_base + mr->usable_size);
+	offset = (pfn << PAGE_SHIFT) - mr->hpa_base;
+	dpa = mr->dpa_base + offset;
+
+	return dpa;
+}
+#endif
-- 
2.26.3