diff options
Diffstat (limited to 'target/linux/bcm27xx/patches-5.4/950-0731-udmabuf-fix-dma-buf-cpu-access.patch')
| -rw-r--r-- | target/linux/bcm27xx/patches-5.4/950-0731-udmabuf-fix-dma-buf-cpu-access.patch | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/target/linux/bcm27xx/patches-5.4/950-0731-udmabuf-fix-dma-buf-cpu-access.patch b/target/linux/bcm27xx/patches-5.4/950-0731-udmabuf-fix-dma-buf-cpu-access.patch new file mode 100644 index 0000000000..14cfe8aed3 --- /dev/null +++ b/target/linux/bcm27xx/patches-5.4/950-0731-udmabuf-fix-dma-buf-cpu-access.patch @@ -0,0 +1,60 @@ +From 153f1e1def226f87cc4c307d2806b000a820f64b Mon Sep 17 00:00:00 2001 +From: Gurchetan Singh <gurchetansingh@chromium.org> +Date: Tue, 17 Dec 2019 15:02:28 -0800 +Subject: [PATCH] udmabuf: fix dma-buf cpu access + +Commit 1ffe09590121fbb3786d6c860acdd200f7ab095c upstream. + +I'm just going to put Chia's review comment here since it sums +the issue rather nicely: + +"(1) Semantically, a dma-buf is in DMA domain. CPU access from the +importer must be surrounded by {begin,end}_cpu_access. This gives the +exporter a chance to move the buffer to the CPU domain temporarily. + +(2) When the exporter itself has other means to do CPU access, it is +only reasonable for the exporter to move the buffer to the CPU domain +before access, and to the DMA domain after access. The exporter can +potentially reuse {begin,end}_cpu_access for that purpose. + +Because of (1), udmabuf does need to implement the +{begin,end}_cpu_access hooks. But "begin" should mean +dma_sync_sg_for_cpu and "end" should mean dma_sync_sg_for_device. + +Because of (2), if userspace wants to continuing accessing through the +memfd mapping, it should call udmabuf's {begin,end}_cpu_access to +avoid cache issues." + +Reported-by: Chia-I Wu <olvaffe@gmail.com> +Suggested-by: Chia-I Wu <olvaffe@gmail.com> +Fixes: 284562e1f348 ("udmabuf: implement begin_cpu_access/end_cpu_access hooks") +Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org> +Link: http://patchwork.freedesktop.org/patch/msgid/20191217230228.453-1-gurchetansingh@chromium.org +Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> +--- + drivers/dma-buf/udmabuf.c | 7 +++---- + 1 file changed, 3 insertions(+), 4 deletions(-) + +--- a/drivers/dma-buf/udmabuf.c ++++ b/drivers/dma-buf/udmabuf.c +@@ -122,9 +122,8 @@ static int begin_cpu_udmabuf(struct dma_ + if (IS_ERR(ubuf->sg)) + return PTR_ERR(ubuf->sg); + } else { +- dma_sync_sg_for_device(dev, ubuf->sg->sgl, +- ubuf->sg->nents, +- direction); ++ dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents, ++ direction); + } + + return 0; +@@ -139,7 +138,7 @@ static int end_cpu_udmabuf(struct dma_bu + if (!ubuf->sg) + return -EINVAL; + +- dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents, direction); ++ dma_sync_sg_for_device(dev, ubuf->sg->sgl, ubuf->sg->nents, direction); + return 0; + } + |