linux-kernel - [PATCH] kernel: dma: let dma use vmalloc area

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Date:   Mon, 27 Nov 2023 11:09:30 +0800
From:   "zhaoyang.huang" <zhaoyang.huang@...soc.com>
To:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>,
        <steve.kang@...soc.com>
Subject: [PATCH] kernel: dma: let dma use vmalloc area

From: Zhaoyang Huang <zhaoyang.huang@...soc.com>

memremap within dma_init_coherent_memory will map the given phys_addr
into vmalloc area if the pa is not found during iterating iomem_resources,
which conflict the rejection of vmalloc area in dma_map_single_attrs.
IMO, it is find to let all valid virtual address be valid for DMA as the
user will keep corresponding RAM safe for transfer.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
---
 include/linux/dma-mapping.h | 12 +++++++-----
 kernel/dma/debug.c          |  4 ----
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f0ccca16a0ac..7a7b87289d55 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -328,12 +328,14 @@ static inline void dma_free_noncoherent(struct device *dev, size_t size,
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-	/* DMA must never operate on areas that might be remapped. */
-	if (dev_WARN_ONCE(dev, is_vmalloc_addr(ptr),
-			  "rejecting DMA map of vmalloc memory\n"))
-		return DMA_MAPPING_ERROR;
+	struct page *page;
+
 	debug_dma_map_single(dev, ptr, size);
-	return dma_map_page_attrs(dev, virt_to_page(ptr), offset_in_page(ptr),
+	if (is_vmalloc_addr(ptr))
+		page = vmalloc_to_page(ptr);
+	else
+		page = virt_to_page(ptr);
+	return dma_map_page_attrs(dev, page, offset_in_page(ptr),
 			size, dir, attrs);
 }
 
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 06366acd27b0..51e1fe9a70aa 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -1198,10 +1198,6 @@ void debug_dma_map_single(struct device *dev, const void *addr,
 	if (!virt_addr_valid(addr))
 		err_printk(dev, NULL, "device driver maps memory from invalid area [addr=%p] [len=%lu]\n",
 			   addr, len);
-
-	if (is_vmalloc_addr(addr))
-		err_printk(dev, NULL, "device driver maps memory from vmalloc area [addr=%p] [len=%lu]\n",
-			   addr, len);
 }
 EXPORT_SYMBOL(debug_dma_map_single);
 
-- 
2.25.1