[RFC PATCH v1 01/18] dma-mapping: query DMA memory type

Leon Romanovsky
2024-07-02T09:10:04Z

From: Leon Romanovsky <leonro@nvidia.com>

Provide an option to query and set DMA memory type so callers who supply
range of pages can perform it only once as the whole range is supposed
to have same memory type.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
include/linux/dma-mapping.h | 20 ++++++++++++++++++++
kernel/dma/mapping.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f693aafe221f..49b99c6e7ec5 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -76,6 +76,20 @@

#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))

+enum dma_memory_types {
+ /* Normal memory without any extra properties like P2P, e.t.c */
+ DMA_MEMORY_TYPE_NORMAL,
+ /* Memory which is p2p capable */
+ DMA_MEMORY_TYPE_P2P,
+ /* Encrypted memory (TDX) */
+ DMA_MEMORY_TYPE_ENCRYPTED,
+};
+
+struct dma_memory_type {
+ enum dma_memory_types type;
+ struct dev_pagemap *p2p_pgmap;
+};
+
#ifdef CONFIG_DMA_API_DEBUG
void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
void debug_dma_map_single(struct device *dev, const void *addr,
@@ -149,6 +163,8 @@ void *dma_vmap_noncontiguous(struct device *dev, size_t size,
void dma_vunmap_noncontiguous(struct device *dev, void *vaddr);
int dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
size_t size, struct sg_table *sgt);
+
+void dma_get_memory_type(struct page *page, struct dma_memory_type *type);
#else /* CONFIG_HAS_DMA */
static inline dma_addr_t dma_map_page_attrs(struct device *dev,
struct page *page, size_t offset, size_t size,
@@ -279,6 +295,10 @@ static inline int dma_mmap_noncontiguous(struct device *dev,
{
return -EINVAL;
}
+static inline void dma_get_memory_type(struct page *page,
+ struct dma_memory_type *type)
+{
+}
#endif /* CONFIG_HAS_DMA */

#if defined(CONFIG_HAS_DMA) && defined(CONFIG_DMA_NEED_SYNC)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 81de84318ccc..877e43b39c06 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -6,6 +6,7 @@
* Copyright (c) 2006 Tejun Heo <teheo@suse.de>
*/
#include <linux/memblock.h> /* for max_pfn */
+#include <linux/memremap.h>
#include <linux/acpi.h>
#include <linux/dma-map-ops.h>
#include <linux/export.h>
@@ -14,6 +15,7 @@
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
+#include <linux/cc_platform.h>
#include "debug.h"
#include "direct.h"

@@ -894,3 +896,31 @@ unsigned long dma_get_merge_boundary(struct device *dev)
return ops->get_merge_boundary(dev);
}
EXPORT_SYMBOL_GPL(dma_get_merge_boundary);
+
+/**
+ * dma_get_memory_type - get the DMA memory type of the page supplied
+ * @page: page to check
+ * @type: memory type of that page
+ *
+ * Return the DMA memory type for the struct page. Pages with the same
+ * memory type can be combined into the same IOVA mapping. Users of the
+ * dma_iova family of functions must seperate the memory they want to map
+ * into same-memory type ranges.
+ */
+void dma_get_memory_type(struct page *page, struct dma_memory_type *type)
+{
+ /* TODO: Rewrite this check to rely on specific struct page flags */
+ if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
+ type->type = DMA_MEMORY_TYPE_ENCRYPTED;
+ return;
+ }
+
+ if (is_pci_p2pdma_page(page)) {
+ type->type = DMA_MEMORY_TYPE_P2P;
+ type->p2p_pgmap = page->pgmap;
+ return;
+ }
+
+ type->type = DMA_MEMORY_TYPE_NORMAL;
+}
+EXPORT_SYMBOL_GPL(dma_get_memory_type);
--
2.45.2