The main use for udmabuf is sending guest memory pages to the host.
It's generally a bad idea to have to separate mappings with different attributes. For example, a WC mapping the guest kernel and cached mapping on the host is problematic.
Add creation time flags so the user has responsibility for the specific use case.
Signed-off-by: Gurchetan Singh gurchetansingh@chromium.org --- drivers/dma-buf/udmabuf.c | 7 ++++++- include/uapi/linux/udmabuf.h | 5 ++++- 2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index b345e91d831a..4ecf2a94fed3 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -186,7 +186,12 @@ static long udmabuf_create(const struct udmabuf_create_list *head, exp_info.ops = &udmabuf_ops; exp_info.size = ubuf->pagecount << PAGE_SHIFT; exp_info.priv = ubuf; - exp_info.flags = O_RDWR; + + if ((head->flags & UDMABUF_FLAGS_PROT_READ) && + (head->flags & UDMABUF_FLAGS_PROT_WRITE)) + exp_info.flags = O_RDWR; + else if (head->flags & UDMABUF_FLAGS_PROT_WRITE) + exp_info.flags = O_WRONLY;
buf = dma_buf_export(&exp_info); if (IS_ERR(buf)) { diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h index 46b6532ed855..21290cb9696c 100644 --- a/include/uapi/linux/udmabuf.h +++ b/include/uapi/linux/udmabuf.h @@ -5,7 +5,10 @@ #include <linux/types.h> #include <linux/ioctl.h>
-#define UDMABUF_FLAGS_CLOEXEC 0x01 +#define UDMABUF_FLAGS_CLOEXEC 0x01 +#define UDMABUF_FLAGS_PROT_NONE 0x02 +#define UDMABUF_FLAGS_PROT_READ 0x04 +#define UDMABUF_FLAGS_PROT_WRITE 0x08
struct udmabuf_create { __u32 memfd;