iommu/pages: Allow sub page sizes to be passed into the allocator

Generally drivers have a specific idea what their HW structure size should
be. In a lot of cases this is related to PAGE_SIZE, but not always. ARM64,
for example, allows a 4K IO page table size on a 64K CPU page table
system.

Currently we don't have any good support for sub page allocations, but
make the API accommodate this by accepting a sub page size from the caller
and rounding up internally.

This is done by moving away from order as the size input and using size:
  size == 1 << (order + PAGE_SHIFT)

Following patches convert drivers away from using order and try to specify
allocation sizes independent of PAGE_SIZE.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/15-v4-c8663abbb606+3f7-iommu_pages_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu-pages.c

@@ -23,24 +23,32 @@ IOPTDESC_MATCH(memcg_data, memcg_data);
 static_assert(sizeof(struct ioptdesc) <= sizeof(struct page));
 
 /**
- * iommu_alloc_pages_node - Allocate a zeroed page of a given order from
- *                          specific NUMA node
+ * iommu_alloc_pages_node_sz - Allocate a zeroed page of a given size from
+ *                             specific NUMA node
  * @nid: memory NUMA node id
  * @gfp: buddy allocator flags
- * @order: page order
+ * @size: Memory size to allocate, rounded up to a power of 2
  *
- * Returns the virtual address of the allocated page. The page must be
- * freed either by calling iommu_free_pages() or via iommu_put_pages_list().
+ * Returns the virtual address of the allocated page. The page must be freed
+ * either by calling iommu_free_pages() or via iommu_put_pages_list(). The
+ * returned allocation is round_up_pow_two(size) big, and is physically aligned
+ * to its size.
  */
-void *iommu_alloc_pages_node(int nid, gfp_t gfp, unsigned int order)
+void *iommu_alloc_pages_node_sz(int nid, gfp_t gfp, size_t size)
 {
-	const unsigned long pgcnt = 1UL << order;
+	unsigned long pgcnt;
 	struct folio *folio;
+	unsigned int order;
 
 	/* This uses page_address() on the memory. */
 	if (WARN_ON(gfp & __GFP_HIGHMEM))
 		return NULL;
 
+	/*
+	 * Currently sub page allocations result in a full page being returned.
+	 */
+	order = get_order(size);
+
 	/*
 	 * __folio_alloc_node() does not handle NUMA_NO_NODE like
 	 * alloc_pages_node() did.
@@ -61,12 +69,13 @@ void *iommu_alloc_pages_node(int nid, gfp_t gfp, unsigned int order)
 	 * This is necessary for the proper accounting as IOMMU state can be
 	 * rather large, i.e. multiple gigabytes in size.
 	 */
+	pgcnt = 1UL << order;
 	mod_node_page_state(folio_pgdat(folio), NR_IOMMU_PAGES, pgcnt);
 	lruvec_stat_mod_folio(folio, NR_SECONDARY_PAGETABLE, pgcnt);
 
 	return folio_address(folio);
 }
-EXPORT_SYMBOL_GPL(iommu_alloc_pages_node);
+EXPORT_SYMBOL_GPL(iommu_alloc_pages_node_sz);
 
 static void __iommu_free_desc(struct ioptdesc *iopt)
 {
@@ -82,7 +91,7 @@ static void __iommu_free_desc(struct ioptdesc *iopt)
  * iommu_free_pages - free pages
  * @virt: virtual address of the page to be freed.
  *
- * The page must have have been allocated by iommu_alloc_pages_node()
+ * The page must have have been allocated by iommu_alloc_pages_node_sz()
  */
 void iommu_free_pages(void *virt)
 {
@@ -96,7 +105,7 @@ EXPORT_SYMBOL_GPL(iommu_free_pages);
  * iommu_put_pages_list - free a list of pages.
  * @list: The list of pages to be freed
  *
- * Frees a list of pages allocated by iommu_alloc_pages_node().
+ * Frees a list of pages allocated by iommu_alloc_pages_node_sz().
  */
 void iommu_put_pages_list(struct iommu_pages_list *list)
 {

drivers/iommu/iommu-pages.h

@@ -46,14 +46,14 @@ static inline struct ioptdesc *virt_to_ioptdesc(void *virt)
 	return folio_ioptdesc(virt_to_folio(virt));
 }
 
-void *iommu_alloc_pages_node(int nid, gfp_t gfp, unsigned int order);
+void *iommu_alloc_pages_node_sz(int nid, gfp_t gfp, size_t size);
 void iommu_free_pages(void *virt);
 void iommu_put_pages_list(struct iommu_pages_list *list);
 
 /**
  * iommu_pages_list_add - add the page to a iommu_pages_list
  * @list: List to add the page to
- * @virt: Address returned from iommu_alloc_pages_node()
+ * @virt: Address returned from iommu_alloc_pages_node_sz()
  */
 static inline void iommu_pages_list_add(struct iommu_pages_list *list,
 					void *virt)
@@ -84,16 +84,48 @@ static inline bool iommu_pages_list_empty(struct iommu_pages_list *list)
 	return list_empty(&list->pages);
 }
 
+/**
+ * iommu_alloc_pages_node - Allocate a zeroed page of a given order from
+ *                          specific NUMA node
+ * @nid: memory NUMA node id
+ * @gfp: buddy allocator flags
+ * @order: page order
+ *
+ * Returns the virtual address of the allocated page.
+ * Prefer to use iommu_alloc_pages_node_lg2()
+ */
+static inline void *iommu_alloc_pages_node(int nid, gfp_t gfp,
+					   unsigned int order)
+{
+	return iommu_alloc_pages_node_sz(nid, gfp, 1 << (order + PAGE_SHIFT));
+}
+
 /**
  * iommu_alloc_pages - allocate a zeroed page of a given order
  * @gfp: buddy allocator flags
  * @order: page order
  *
  * returns the virtual address of the allocated page
+ * Prefer to use iommu_alloc_pages_lg2()
  */
 static inline void *iommu_alloc_pages(gfp_t gfp, int order)
 {
-	return iommu_alloc_pages_node(NUMA_NO_NODE, gfp, order);
+	return iommu_alloc_pages_node_sz(NUMA_NO_NODE, gfp,
+					 1 << (order + PAGE_SHIFT));
+}
+
+/**
+ * iommu_alloc_pages_sz - Allocate a zeroed page of a given size from
+ *                          specific NUMA node
+ * @nid: memory NUMA node id
+ * @gfp: buddy allocator flags
+ * @size: Memory size to allocate, this is rounded up to a power of 2
+ *
+ * Returns the virtual address of the allocated page.
+ */
+static inline void *iommu_alloc_pages_sz(gfp_t gfp, size_t size)
+{
+	return iommu_alloc_pages_node_sz(NUMA_NO_NODE, gfp, size);
 }
 
 /**
@@ -102,10 +134,11 @@ static inline void *iommu_alloc_pages(gfp_t gfp, int order)
  * @gfp: buddy allocator flags
  *
  * returns the virtual address of the allocated page
+ * Prefer to use iommu_alloc_pages_node_lg2()
  */
 static inline void *iommu_alloc_page_node(int nid, gfp_t gfp)
 {
-	return iommu_alloc_pages_node(nid, gfp, 0);
+	return iommu_alloc_pages_node_sz(nid, gfp, PAGE_SIZE);
 }
 
 /**
@@ -113,10 +146,11 @@ static inline void *iommu_alloc_page_node(int nid, gfp_t gfp)
  * @gfp: buddy allocator flags
  *
  * returns the virtual address of the allocated page
+ * Prefer to use iommu_alloc_pages_lg2()
  */
 static inline void *iommu_alloc_page(gfp_t gfp)
 {
-	return iommu_alloc_pages_node(NUMA_NO_NODE, gfp, 0);
+	return iommu_alloc_pages_node_sz(NUMA_NO_NODE, gfp, PAGE_SIZE);
 }
 
 #endif	/* __IOMMU_PAGES_H */

include/linux/iommu.h

@@ -342,9 +342,9 @@ typedef unsigned int ioasid_t;
 #define IOMMU_DIRTY_NO_CLEAR (1 << 0)
 
 /*
- * Pages allocated through iommu_alloc_pages_node() can be placed on this list
- * using iommu_pages_list_add(). Note: ONLY pages from iommu_alloc_pages_node()
- * can be used this way!
+ * Pages allocated through iommu_alloc_pages_node_sz() can be placed on this
+ * list using iommu_pages_list_add(). Note: ONLY pages from
+ * iommu_alloc_pages_node_sz() can be used this way!
  */
 struct iommu_pages_list {
 	struct list_head pages;