linux-kernel - [RFC PATCH 1/6] udmabuf: try fix udmabuf vmap

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Message-ID: <20250327092922.536-2-link@vivo.com>
Date: Thu, 27 Mar 2025 17:28:28 +0800
From: Huan Yang <link@...o.com>
To: bingbu.cao@...ux.intel.com,
	Matthew Wilcox <willy@...radead.org>,
	Christoph Hellwig <hch@....de>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Shuah Khan <shuah@...nel.org>,
	Huan Yang <link@...o.com>,
	linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-media@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org,
	linux-mm@...ck.org,
	linux-kselftest@...r.kernel.org
Cc: opensource.kernel@...o.com
Subject: [RFC PATCH 1/6] udmabuf: try fix udmabuf vmap

vmap_pfn design to only allow none page based pfn map.

This patch try simple copy pfn vmap code to fix it.

Fix vunmap_udmabuf fix match with vmap_udmabuf, use vunmap.

Signed-off-by: Huan Yang <link@...o.com>
---
 drivers/dma-buf/udmabuf.c | 49 +++++++++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 4 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index cc7398cc17d6..2dfe639230dc 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -106,6 +106,49 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
 	return 0;
 }
 
+struct udmabuf_pfn_data {
+	unsigned long *pfns;
+	pgprot_t prot;
+	unsigned int idx;
+};
+
+static int udmabuf_vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
+{
+	struct udmabuf_pfn_data *data = private;
+	pte_t ptent;
+
+	ptent = pte_mkspecial(pfn_pte(data->pfns[data->idx], data->prot));
+	set_pte_at(&init_mm, addr, pte, ptent);
+
+	data->idx++;
+	return 0;
+}
+
+static void *udmabuf_vmap_pfn(unsigned long *pfns, unsigned int count,
+			      pgprot_t prot)
+{
+	struct udmabuf_pfn_data data = { .pfns = pfns,
+					 .prot = pgprot_nx(prot) };
+	struct vm_struct *area;
+
+	area = get_vm_area_caller(count * PAGE_SIZE, 0,
+				  __builtin_return_address(0));
+	if (!area)
+		return NULL;
+
+	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
+				count * PAGE_SIZE, udmabuf_vmap_pfn_apply,
+				&data)) {
+		free_vm_area(area);
+		return NULL;
+	}
+
+	flush_cache_vmap((unsigned long)area->addr,
+			 (unsigned long)area->addr + count * PAGE_SIZE);
+
+	return area->addr;
+}
+
 static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
 {
 	struct udmabuf *ubuf = buf->priv;
@@ -130,7 +173,7 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
 		pfns[pg] = pfn;
 	}
 
-	vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
+	vaddr = udmabuf_vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
 	kvfree(pfns);
 	if (!vaddr)
 		return -EINVAL;
@@ -141,11 +184,9 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
 
 static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
 {
-	struct udmabuf *ubuf = buf->priv;
-
 	dma_resv_assert_held(buf->resv);
 
-	vm_unmap_ram(map->vaddr, ubuf->pagecount);
+	vunmap(map->vaddr);
 }
 
 static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
-- 
2.48.1