[PATCH liburing 2/2] examples/zcrx: udmabuf backed areas

[Pavel Begunkov <asml.silence@gmail.com>]

Add an example of how to create dmabuf backed area. For that we use
udmabuf and mmap it into user space, however in more realistic scenarios
won't have direct access to the memory and will need to use dmabuf
provider specific api, e.g. OpenCl.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 examples/zcrx.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/examples/zcrx.c b/examples/zcrx.c
index 6b06e4fa..c5e1b42f 100644
--- a/examples/zcrx.c
+++ b/examples/zcrx.c
@@ -37,6 +37,10 @@
 #include <sys/wait.h>
 #include <linux/mman.h>
 
+#include <linux/memfd.h>
+#include <linux/dma-buf.h>
+#include <linux/udmabuf.h>
+
 #include "liburing.h"
 #include "helpers.h"
 
@@ -56,6 +60,7 @@ static long page_size;
 enum {
 	AREA_TYPE_NORMAL,
 	AREA_TYPE_HUGE_PAGES,
+	AREA_TYPE_DMABUF,
 	__AREA_TYPE_MAX,
 };
 
@@ -83,6 +88,9 @@ static bool stop;
 static size_t received;
 static __u32 zcrx_id;
 
+static int dmabuf_fd;
+static int memfd;
+
 static inline size_t get_refill_ring_size(unsigned int rq_entries)
 {
 	ring_size = rq_entries * sizeof(struct io_uring_zcrx_rqe);
@@ -91,11 +99,58 @@ static inline size_t get_refill_ring_size(unsigned int rq_entries)
 	return T_ALIGN_UP(ring_size, page_size);
 }
 
+static void zcrx_populate_area_udmabuf(struct io_uring_zcrx_area_reg *area_reg)
+{
+	struct udmabuf_create create;
+	int ret, devfd;
+
+	devfd = open("/dev/udmabuf", O_RDWR);
+	if (devfd < 0)
+		t_error(1, devfd, "Failed to open udmabuf dev");
+
+	memfd = memfd_create("udmabuf-test", MFD_ALLOW_SEALING);
+	if (memfd < 0)
+		t_error(1, memfd, "Failed to open udmabuf dev");
+
+	ret = fcntl(memfd, F_ADD_SEALS, F_SEAL_SHRINK);
+	if (ret < 0)
+		t_error(1, 0, "Failed to set seals");
+
+	ret = ftruncate(memfd, AREA_SIZE);
+	if (ret == -1)
+		t_error(1, 0, "Failed to resize udmabuf");
+
+	memset(&create, 0, sizeof(create));
+	create.memfd = memfd;
+	create.offset = 0;
+	create.size = AREA_SIZE;
+	dmabuf_fd = ioctl(devfd, UDMABUF_CREATE, &create);
+	if (dmabuf_fd < 0)
+		t_error(1, dmabuf_fd, "Failed to create udmabuf");
+
+	area_ptr = mmap(NULL, AREA_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
+			dmabuf_fd, 0);
+	if (area_ptr == MAP_FAILED)
+		t_error(1, 0, "Failed to mmap udmabuf");
+
+	memset(area_reg, 0, sizeof(*area_reg));
+	area_reg->addr = 0; /* offset into dmabuf */
+	area_reg->len = AREA_SIZE;
+	area_reg->flags |= IORING_ZCRX_AREA_DMABUF;
+	area_reg->dmabuf_fd = dmabuf_fd;
+
+	close(devfd);
+}
+
 static void zcrx_populate_area(struct io_uring_zcrx_area_reg *area_reg)
 {
 	unsigned flags = MAP_PRIVATE | MAP_ANONYMOUS;
 	unsigned prot = PROT_READ | PROT_WRITE;
 
+	if (cfg_area_type == AREA_TYPE_DMABUF) {
+		zcrx_populate_area_udmabuf(area_reg);
+		return;
+	}
 	if (cfg_area_type == AREA_TYPE_NORMAL) {
 		area_ptr = mmap(NULL, AREA_SIZE, prot,
 				flags, 0, 0);
-- 
2.48.1