v4.19.13 snapshot.
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
new file mode 100644
index 0000000..f91f9e7
--- /dev/null
+++ b/include/linux/memremap.h
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MEMREMAP_H_
+#define _LINUX_MEMREMAP_H_
+#include <linux/ioport.h>
+#include <linux/percpu-refcount.h>
+
+#include <asm/pgtable.h>
+
+struct resource;
+struct device;
+
+/**
+ * struct vmem_altmap - pre-allocated storage for vmemmap_populate
+ * @base_pfn: base of the entire dev_pagemap mapping
+ * @reserve: pages mapped, but reserved for driver use (relative to @base)
+ * @free: free pages set aside in the mapping for memmap storage
+ * @align: pages reserved to meet allocation alignments
+ * @alloc: track pages consumed, private to vmemmap_populate()
+ */
+struct vmem_altmap {
+ const unsigned long base_pfn;
+ const unsigned long reserve;
+ unsigned long free;
+ unsigned long align;
+ unsigned long alloc;
+};
+
+/*
+ * Specialize ZONE_DEVICE memory into multiple types each having differents
+ * usage.
+ *
+ * MEMORY_DEVICE_PRIVATE:
+ * Device memory that is not directly addressable by the CPU: CPU can neither
+ * read nor write private memory. In this case, we do still have struct pages
+ * backing the device memory. Doing so simplifies the implementation, but it is
+ * important to remember that there are certain points at which the struct page
+ * must be treated as an opaque object, rather than a "normal" struct page.
+ *
+ * A more complete discussion of unaddressable memory may be found in
+ * include/linux/hmm.h and Documentation/vm/hmm.rst.
+ *
+ * MEMORY_DEVICE_PUBLIC:
+ * Device memory that is cache coherent from device and CPU point of view. This
+ * is use on platform that have an advance system bus (like CAPI or CCIX). A
+ * driver can hotplug the device memory using ZONE_DEVICE and with that memory
+ * type. Any page of a process can be migrated to such memory. However no one
+ * should be allow to pin such memory so that it can always be evicted.
+ *
+ * MEMORY_DEVICE_FS_DAX:
+ * Host memory that has similar access semantics as System RAM i.e. DMA
+ * coherent and supports page pinning. In support of coordinating page
+ * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
+ * wakeup event whenever a page is unpinned and becomes idle. This
+ * wakeup is used to coordinate physical address space management (ex:
+ * fs truncate/hole punch) vs pinned pages (ex: device dma).
+ */
+enum memory_type {
+ MEMORY_DEVICE_PRIVATE = 1,
+ MEMORY_DEVICE_PUBLIC,
+ MEMORY_DEVICE_FS_DAX,
+};
+
+/*
+ * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
+ * callbacks:
+ * page_fault()
+ * page_free()
+ *
+ * Additional notes about MEMORY_DEVICE_PRIVATE may be found in
+ * include/linux/hmm.h and Documentation/vm/hmm.rst. There is also a brief
+ * explanation in include/linux/memory_hotplug.h.
+ *
+ * The page_fault() callback must migrate page back, from device memory to
+ * system memory, so that the CPU can access it. This might fail for various
+ * reasons (device issues, device have been unplugged, ...). When such error
+ * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
+ * set the CPU page table entry to "poisoned".
+ *
+ * Note that because memory cgroup charges are transferred to the device memory,
+ * this should never fail due to memory restrictions. However, allocation
+ * of a regular system page might still fail because we are out of memory. If
+ * that happens, the page_fault() callback must return VM_FAULT_OOM.
+ *
+ * The page_fault() callback can also try to migrate back multiple pages in one
+ * chunk, as an optimization. It must, however, prioritize the faulting address
+ * over all the others.
+ *
+ *
+ * The page_free() callback is called once the page refcount reaches 1
+ * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
+ * This allows the device driver to implement its own memory management.)
+ *
+ * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
+ */
+typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
+ unsigned long addr,
+ const struct page *page,
+ unsigned int flags,
+ pmd_t *pmdp);
+typedef void (*dev_page_free_t)(struct page *page, void *data);
+
+/**
+ * struct dev_pagemap - metadata for ZONE_DEVICE mappings
+ * @page_fault: callback when CPU fault on an unaddressable device page
+ * @page_free: free page callback when page refcount reaches 1
+ * @altmap: pre-allocated/reserved memory for vmemmap allocations
+ * @res: physical address range covered by @ref
+ * @ref: reference count that pins the devm_memremap_pages() mapping
+ * @dev: host device of the mapping for debug
+ * @data: private data pointer for page_free()
+ * @type: memory type: see MEMORY_* in memory_hotplug.h
+ */
+struct dev_pagemap {
+ dev_page_fault_t page_fault;
+ dev_page_free_t page_free;
+ struct vmem_altmap altmap;
+ bool altmap_valid;
+ struct resource res;
+ struct percpu_ref *ref;
+ struct device *dev;
+ void *data;
+ enum memory_type type;
+};
+
+#ifdef CONFIG_ZONE_DEVICE
+void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
+struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
+ struct dev_pagemap *pgmap);
+
+unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
+void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
+#else
+static inline void *devm_memremap_pages(struct device *dev,
+ struct dev_pagemap *pgmap)
+{
+ /*
+ * Fail attempts to call devm_memremap_pages() without
+ * ZONE_DEVICE support enabled, this requires callers to fall
+ * back to plain devm_memremap() based on config
+ */
+ WARN_ON_ONCE(1);
+ return ERR_PTR(-ENXIO);
+}
+
+static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
+ struct dev_pagemap *pgmap)
+{
+ return NULL;
+}
+
+static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+{
+ return 0;
+}
+
+static inline void vmem_altmap_free(struct vmem_altmap *altmap,
+ unsigned long nr_pfns)
+{
+}
+#endif /* CONFIG_ZONE_DEVICE */
+
+static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
+{
+ if (pgmap)
+ percpu_ref_put(pgmap->ref);
+}
+#endif /* _LINUX_MEMREMAP_H_ */