[PATCH net-next 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

Add -b <bytes> to request a non-default niov size via
NETDEV_A_DMABUF_RX_BUF_SIZE. When the value exceeds PAGE_SIZE,
udmabuf_alloc() switches to an MFD_HUGETLB-backed memfd so each 2 MB
hugepage produces one naturally-aligned sg entry.

Reject values > 2 MB up front: MFD_HUGETLB + udmabuf can only guarantee
2 MB per sg entry (one hugepage), so a larger rx_buf_size would fail the
per-sg length/alignment check.

Add CONFIG_HUGETLBFS=y to drivers/net/hw/config so the new path is
reachable in the CI kernels built for these tests.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
 tools/testing/selftests/drivers/net/hw/config     |  1 +
 tools/testing/selftests/drivers/net/hw/ncdevmem.c | 49 +++++++++++++++++++++--
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/hw/config b/tools/testing/selftests/drivers/net/hw/config
index b9f406dd7282..388721bee553 100644
--- a/tools/testing/selftests/drivers/net/hw/config
+++ b/tools/testing/selftests/drivers/net/hw/config
@@ -3,6 +3,7 @@ CONFIG_FAIL_FUNCTION=y
 CONFIG_FAULT_INJECTION=y
 CONFIG_FAULT_INJECTION_DEBUG_FS=y
 CONFIG_FUNCTION_ERROR_INJECTION=y
+CONFIG_HUGETLBFS=y
 CONFIG_INET6_ESP=y
 CONFIG_INET6_ESP_OFFLOAD=y
 CONFIG_INET_ESP=y
diff --git a/tools/testing/selftests/drivers/net/hw/ncdevmem.c b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
index d96e8a3b5a65..325c128191e2 100644
--- a/tools/testing/selftests/drivers/net/hw/ncdevmem.c
+++ b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
@@ -61,6 +61,7 @@
 #include <sys/time.h>
 
 #include <linux/memfd.h>
+#include <sys/param.h>
 #include <linux/dma-buf.h>
 #include <linux/errqueue.h>
 #include <linux/udmabuf.h>
@@ -79,6 +80,7 @@
 #define PAGE_SHIFT 12
 #define TEST_PREFIX "ncdevmem"
 #define NUM_PAGES 16000
+#define MB(x) ((x) << 20)
 
 #ifndef MSG_SOCK_DEVMEM
 #define MSG_SOCK_DEVMEM 0x2000000
@@ -100,6 +102,7 @@ static unsigned int dmabuf_id;
 static uint32_t tx_dmabuf_id;
 static int waittime_ms = 500;
 static bool fail_on_linear;
+static uint32_t rx_buf_size;
 
 /* System state loaded by current_config_load() */
 #define MAX_FLOWS	8
@@ -142,6 +145,7 @@ static struct memory_buffer *udmabuf_alloc(size_t size)
 {
 	struct udmabuf_create create;
 	struct memory_buffer *ctx;
+	unsigned int memfd_flags;
 	int ret;
 
 	ctx = malloc(sizeof(*ctx));
@@ -156,9 +160,14 @@ static struct memory_buffer *udmabuf_alloc(size_t size)
 		goto err_free_ctx;
 	}
 
-	ctx->memfd = memfd_create("udmabuf-test", MFD_ALLOW_SEALING);
+	memfd_flags = MFD_ALLOW_SEALING;
+	if (rx_buf_size > (uint32_t)getpagesize())
+		memfd_flags |= MFD_HUGETLB | MFD_HUGE_2MB;
+
+	ctx->memfd = memfd_create("udmabuf-test", memfd_flags);
 	if (ctx->memfd < 0) {
-		pr_err("[skip,no-memfd]");
+		pr_err("[skip,no-memfd%s]",
+		       (memfd_flags & MFD_HUGETLB) ? " (need hugepages)" : "");
 		goto err_close_dev;
 	}
 
@@ -168,6 +177,11 @@ static struct memory_buffer *udmabuf_alloc(size_t size)
 		goto err_close_memfd;
 	}
 
+	if (memfd_flags & MFD_HUGETLB) {
+		size = roundup(size, MB(2));
+		ctx->size = size;
+	}
+
 	ret = ftruncate(ctx->memfd, size);
 	if (ret == -1) {
 		pr_err("[FAIL,memfd-truncate]");
@@ -699,6 +713,8 @@ static int bind_rx_queue(unsigned int ifindex, unsigned int dmabuf_fd,
 	netdev_bind_rx_req_set_ifindex(req, ifindex);
 	netdev_bind_rx_req_set_fd(req, dmabuf_fd);
 	__netdev_bind_rx_req_set_queues(req, queues, n_queue_index);
+	if (rx_buf_size)
+		netdev_bind_rx_req_set_rx_buf_size(req, rx_buf_size);
 
 	rsp = netdev_bind_rx(*ys, req);
 	if (!rsp) {
@@ -1411,7 +1427,7 @@ int main(int argc, char *argv[])
 	int is_server = 0, opt;
 	int ret, err = 1;
 
-	while ((opt = getopt(argc, argv, "Lls:c:p:v:q:t:f:z:n")) != -1) {
+	while ((opt = getopt(argc, argv, "Lls:c:p:v:q:t:f:z:nb:")) != -1) {
 		switch (opt) {
 		case 'L':
 			fail_on_linear = true;
@@ -1446,6 +1462,33 @@ int main(int argc, char *argv[])
 		case 'n':
 			skip_config = 1;
 			break;
+		case 'b': {
+			char *endp;
+			unsigned long val;
+
+			errno = 0;
+			val = strtoul(optarg, &endp, 0);
+			if (errno || endp == optarg || *endp || val == 0 ||
+			    val > UINT32_MAX) {
+				pr_err("invalid rx_buf_size: %s", optarg);
+				return 1;
+			}
+			if (val & (val - 1)) {
+				pr_err("rx_buf_size must be a power of 2");
+				return 1;
+			}
+			if (val < (unsigned long)getpagesize()) {
+				pr_err("rx_buf_size must be >= PAGE_SIZE (%d)",
+				       getpagesize());
+				return 1;
+			}
+			if (val > MB(2)) {
+				pr_err("rx_buf_size > 2 MB not supported");
+				return 1;
+			}
+			rx_buf_size = val;
+			break;
+		}
 		case '?':
 			fprintf(stderr, "unknown option: %c\n", optopt);
 			break;

-- 
2.53.0-Meta