[PATCH v1 08/16] kmsan: convert kmsan_handle_dma to use physical addresses

[Leon Romanovsky <leon@kernel.org>]

From: Leon Romanovsky <leonro@nvidia.com>

Convert the KMSAN DMA handling function from page-based to physical
address-based interface.

The refactoring renames kmsan_handle_dma() parameters from accepting
(struct page *page, size_t offset, size_t size) to (phys_addr_t phys,
size_t size). A PFN_VALID check is added to prevent KMSAN operations
on non-page memory, preventing from non struct page backed address,

As part of this change, support for highmem addresses is implemented
using kmap_local_page() to handle both lowmem and highmem regions
properly. All callers throughout the codebase are updated to use the
new phys_addr_t based interface.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/virtio/virtio_ring.c |  4 ++--
 include/linux/kmsan.h        | 12 +++++++-----
 kernel/dma/mapping.c         |  2 +-
 mm/kmsan/hooks.c             | 36 +++++++++++++++++++++++++++++-------
 tools/virtio/linux/kmsan.h   |  2 +-
 5 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index f5062061c4084..c147145a65930 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -378,7 +378,7 @@ static int vring_map_one_sg(const struct vring_virtqueue *vq, struct scatterlist
 		 * is initialized by the hardware. Explicitly check/unpoison it
 		 * depending on the direction.
 		 */
-		kmsan_handle_dma(sg_page(sg), sg->offset, sg->length, direction);
+		kmsan_handle_dma(sg_phys(sg), sg->length, direction);
 		*addr = (dma_addr_t)sg_phys(sg);
 		return 0;
 	}
@@ -3157,7 +3157,7 @@ dma_addr_t virtqueue_dma_map_single_attrs(struct virtqueue *_vq, void *ptr,
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
 	if (!vq->use_dma_api) {
-		kmsan_handle_dma(virt_to_page(ptr), offset_in_page(ptr), size, dir);
+		kmsan_handle_dma(virt_to_phys(ptr), size, dir);
 		return (dma_addr_t)virt_to_phys(ptr);
 	}
 
diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
index 2b1432cc16d59..6f27b9824ef77 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -182,8 +182,7 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
 
 /**
  * kmsan_handle_dma() - Handle a DMA data transfer.
- * @page:   first page of the buffer.
- * @offset: offset of the buffer within the first page.
+ * @phys:   physical address of the buffer.
  * @size:   buffer size.
  * @dir:    one of possible dma_data_direction values.
  *
@@ -191,8 +190,11 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
  * * checks the buffer, if it is copied to device;
  * * initializes the buffer, if it is copied from device;
  * * does both, if this is a DMA_BIDIRECTIONAL transfer.
+ *
+ * The function handles page lookup internally and supports both lowmem
+ * and highmem addresses.
  */
-void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+void kmsan_handle_dma(phys_addr_t phys, size_t size,
 		      enum dma_data_direction dir);
 
 /**
@@ -372,8 +374,8 @@ static inline void kmsan_iounmap_page_range(unsigned long start,
 {
 }
 
-static inline void kmsan_handle_dma(struct page *page, size_t offset,
-				    size_t size, enum dma_data_direction dir)
+static inline void kmsan_handle_dma(phys_addr_t phys, size_t size,
+				    enum dma_data_direction dir)
 {
 }
 
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 80481a873340a..709405d46b2b4 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -172,7 +172,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
 	else
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
-	kmsan_handle_dma(page, offset, size, dir);
+	kmsan_handle_dma(phys, size, dir);
 	trace_dma_map_phys(dev, phys, addr, size, dir, attrs);
 	debug_dma_map_phys(dev, phys, size, dir, addr, attrs);
 
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 97de3d6194f07..eab7912a3bf05 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -336,25 +336,48 @@ static void kmsan_handle_dma_page(const void *addr, size_t size,
 }
 
 /* Helper function to handle DMA data transfers. */
-void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+void kmsan_handle_dma(phys_addr_t phys, size_t size,
 		      enum dma_data_direction dir)
 {
 	u64 page_offset, to_go, addr;
+	struct page *page;
+	void *kaddr;
 
-	if (PageHighMem(page))
+	if (!pfn_valid(PHYS_PFN(phys)))
 		return;
-	addr = (u64)page_address(page) + offset;
+
+	page = phys_to_page(phys);
+	page_offset = offset_in_page(phys);
+
 	/*
 	 * The kernel may occasionally give us adjacent DMA pages not belonging
 	 * to the same allocation. Process them separately to avoid triggering
 	 * internal KMSAN checks.
 	 */
 	while (size > 0) {
-		page_offset = offset_in_page(addr);
 		to_go = min(PAGE_SIZE - page_offset, (u64)size);
+
+		if (PageHighMem(page))
+			/* Handle highmem pages using kmap */
+			kaddr = kmap_local_page(page);
+		else
+			/* Lowmem pages can be accessed directly */
+			kaddr = page_address(page);
+
+		addr = (u64)kaddr + page_offset;
 		kmsan_handle_dma_page((void *)addr, to_go, dir);
-		addr += to_go;
+
+		if (PageHighMem(page))
+			kunmap_local(page);
+
+		phys += to_go;
 		size -= to_go;
+
+		/* Move to next page if needed */
+		if (size > 0) {
+			page = phys_to_page(phys);
+			page_offset = offset_in_page(phys);
+		}
 	}
 }
 EXPORT_SYMBOL_GPL(kmsan_handle_dma);
@@ -366,8 +389,7 @@ void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
 	int i;
 
 	for_each_sg(sg, item, nents, i)
-		kmsan_handle_dma(sg_page(item), item->offset, item->length,
-				 dir);
+		kmsan_handle_dma(sg_phys(item), item->length, dir);
 }
 
 /* Functions from kmsan-checks.h follow. */
diff --git a/tools/virtio/linux/kmsan.h b/tools/virtio/linux/kmsan.h
index 272b5aa285d5a..6cd2e3efd03dc 100644
--- a/tools/virtio/linux/kmsan.h
+++ b/tools/virtio/linux/kmsan.h
@@ -4,7 +4,7 @@
 
 #include <linux/gfp.h>
 
-inline void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+inline void kmsan_handle_dma(phys_addr_t phys, size_t size,
 			     enum dma_data_direction dir)
 {
 }
-- 
2.50.1