Merge branch 'xsk-tailroom-reservation-and-mtu-validation'

Maciej Fijalkowski says:

====================
xsk: tailroom reservation and MTU validation

here we fix a long-standing issue regarding multi-buffer scenario in ZC
mode - we have not been providing space at the end of the buffer where
multi-buffer XDP works on skb_shared_info. This has been brought to our
attention via [0].

Unaligned mode does not get any specific treatment, it is user's
responsibility to properly handle XSK addresses in queues.

With adjustments included here in this set against xskxceiver I have
been able to pass the full test suite on ice.

[0]: https://community.intel.com/t5/Ethernet-Products/X710-XDP-Packet-Corruption-Issue-DRV-MODE-Zero-Copy-Multi-Buffer/m-p/1724208
====================

Link: https://patch.msgid.link/20260402154958.562179-1-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

5 files changed, 94 insertions, 30 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_xsk.c b/tools/testing/selftests/bpf/prog_tests/test_xsk.c
index 7e38ec6e656b..7950c504ed28 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_xsk.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_xsk.c
@@ -179,25 +179,6 @@ int xsk_configure_socket(struct xsk_socket_info *xsk, struct xsk_umem_info *umem
 	return xsk_socket__create(&xsk->xsk, ifobject->ifindex, 0, umem->umem, rxr, txr, &cfg);
 }
 
-#define MAX_SKB_FRAGS_PATH "/proc/sys/net/core/max_skb_frags"
-static unsigned int get_max_skb_frags(void)
-{
-	unsigned int max_skb_frags = 0;
-	FILE *file;
-
-	file = fopen(MAX_SKB_FRAGS_PATH, "r");
-	if (!file) {
-		ksft_print_msg("Error opening %s\n", MAX_SKB_FRAGS_PATH);
-		return 0;
-	}
-
-	if (fscanf(file, "%u", &max_skb_frags) != 1)
-		ksft_print_msg("Error reading %s\n", MAX_SKB_FRAGS_PATH);
-
-	fclose(file);
-	return max_skb_frags;
-}
-
 static int set_ring_size(struct ifobject *ifobj)
 {
 	int ret;
@@ -1978,15 +1959,17 @@ int testapp_headroom(struct test_spec *test)
 
 int testapp_stats_rx_dropped(struct test_spec *test)
 {
+	u32 umem_tr = test->ifobj_tx->umem_tailroom;
+
 	if (test->mode == TEST_MODE_ZC) {
 		ksft_print_msg("Can not run RX_DROPPED test for ZC mode\n");
 		return TEST_SKIP;
 	}
 
-	if (pkt_stream_replace_half(test, MIN_PKT_SIZE * 4, 0))
+	if (pkt_stream_replace_half(test, (MIN_PKT_SIZE * 3) + umem_tr, 0))
 		return TEST_FAILURE;
 	test->ifobj_rx->umem->frame_headroom = test->ifobj_rx->umem->frame_size -
-		XDP_PACKET_HEADROOM - MIN_PKT_SIZE * 3;
+		XDP_PACKET_HEADROOM - (MIN_PKT_SIZE * 2) - umem_tr;
 	if (pkt_stream_receive_half(test))
 		return TEST_FAILURE;
 	test->ifobj_rx->validation_func = validate_rx_dropped;
@@ -2242,11 +2225,7 @@ int testapp_too_many_frags(struct test_spec *test)
 	if (test->mode == TEST_MODE_ZC) {
 		max_frags = test->ifobj_tx->xdp_zc_max_segs;
 	} else {
-		max_frags = get_max_skb_frags();
-		if (!max_frags) {
-			ksft_print_msg("Can't get MAX_SKB_FRAGS from system, using default (17)\n");
-			max_frags = 17;
-		}
+		max_frags = test->ifobj_tx->max_skb_frags;
 		max_frags += 1;
 	}
 
@@ -2551,16 +2530,34 @@ int testapp_adjust_tail_shrink_mb(struct test_spec *test)
 
 int testapp_adjust_tail_grow(struct test_spec *test)
 {
+	if (test->mode == TEST_MODE_SKB)
+		return TEST_SKIP;
+
 	/* Grow by 4 bytes for testing purpose */
 	return testapp_adjust_tail(test, 4, MIN_PKT_SIZE * 2);
 }
 
 int testapp_adjust_tail_grow_mb(struct test_spec *test)
 {
+	u32 grow_size;
+
+	if (test->mode == TEST_MODE_SKB)
+		return TEST_SKIP;
+
+	/* worst case scenario is when underlying setup will work on 3k
+	 * buffers, let us account for it; given that we will use 6k as
+	 * pkt_len, expect that it will be broken down to 2 descs each
+	 * with 3k payload;
+	 *
+	 * 4k is truesize, 3k payload, 256 HR, 320 TR;
+	 */
+	grow_size = XSK_UMEM__MAX_FRAME_SIZE -
+		    XSK_UMEM__LARGE_FRAME_SIZE -
+		    XDP_PACKET_HEADROOM -
+		    test->ifobj_tx->umem_tailroom;
 	test->mtu = MAX_ETH_JUMBO_SIZE;
-	/* Grow by (frag_size - last_frag_Size) - 1 to stay inside the last fragment */
-	return testapp_adjust_tail(test, (XSK_UMEM__MAX_FRAME_SIZE / 2) - 1,
-				   XSK_UMEM__LARGE_FRAME_SIZE * 2);
+
+	return testapp_adjust_tail(test, grow_size, XSK_UMEM__LARGE_FRAME_SIZE * 2);
 }
 
 int testapp_tx_queue_consumer(struct test_spec *test)
diff --git a/tools/testing/selftests/bpf/prog_tests/test_xsk.h b/tools/testing/selftests/bpf/prog_tests/test_xsk.h
index 8fc78a057de0..1ab8aee4ce56 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_xsk.h
+++ b/tools/testing/selftests/bpf/prog_tests/test_xsk.h
@@ -31,6 +31,9 @@
 #define SOCK_RECONF_CTR			10
 #define USLEEP_MAX			10000
 
+#define MAX_SKB_FRAGS_PATH "/proc/sys/net/core/max_skb_frags"
+#define SMP_CACHE_BYTES_PATH "/sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size"
+
 extern bool opt_verbose;
 #define print_verbose(x...) do { if (opt_verbose) ksft_print_msg(x); } while (0)
 
@@ -45,6 +48,24 @@ static inline u64 ceil_u64(u64 a, u64 b)
 	return (a + b - 1) / b;
 }
 
+static inline unsigned int read_procfs_val(const char *path)
+{
+	unsigned int read_val = 0;
+	FILE *file;
+
+	file = fopen(path, "r");
+	if (!file) {
+		ksft_print_msg("Error opening %s\n", path);
+		return 0;
+	}
+
+	if (fscanf(file, "%u", &read_val) != 1)
+		ksft_print_msg("Error reading %s\n", path);
+
+	fclose(file);
+	return read_val;
+}
+
 /* Simple test */
 enum test_mode {
 	TEST_MODE_SKB,
@@ -115,6 +136,8 @@ struct ifobject {
 	int mtu;
 	u32 bind_flags;
 	u32 xdp_zc_max_segs;
+	u32 umem_tailroom;
+	u32 max_skb_frags;
 	bool tx_on;
 	bool rx_on;
 	bool use_poll;
diff --git a/tools/testing/selftests/bpf/prog_tests/xsk.c b/tools/testing/selftests/bpf/prog_tests/xsk.c
index dd4c35c0e428..6e2f63ee2a6c 100644
--- a/tools/testing/selftests/bpf/prog_tests/xsk.c
+++ b/tools/testing/selftests/bpf/prog_tests/xsk.c
@@ -62,6 +62,7 @@ int configure_ifobj(struct ifobject *tx, struct ifobject *rx)
 
 static void test_xsk(const struct test_spec *test_to_run, enum test_mode mode)
 {
+	u32 max_frags, umem_tailroom, cache_line_size;
 	struct ifobject *ifobj_tx, *ifobj_rx;
 	struct test_spec test;
 	int ret;
@@ -84,6 +85,24 @@ static void test_xsk(const struct test_spec *test_to_run, enum test_mode mode)
 		ifobj_tx->set_ring.default_rx = ifobj_tx->ring.rx_pending;
 	}
 
+	cache_line_size = read_procfs_val(SMP_CACHE_BYTES_PATH);
+	if (!cache_line_size)
+		cache_line_size = 64;
+
+	max_frags = read_procfs_val(MAX_SKB_FRAGS_PATH);
+	if (!max_frags)
+		max_frags = 17;
+
+	ifobj_tx->max_skb_frags = max_frags;
+	ifobj_rx->max_skb_frags = max_frags;
+
+	/* 48 bytes is a part of skb_shared_info w/o frags array;
+	 * 16 bytes is sizeof(skb_frag_t)
+	 */
+	umem_tailroom = ALIGN(48 + (max_frags * 16), cache_line_size);
+	ifobj_tx->umem_tailroom = umem_tailroom;
+	ifobj_rx->umem_tailroom = umem_tailroom;
+
 	if (!ASSERT_OK(init_iface(ifobj_rx, worker_testapp_validate_rx), "init RX"))
 		goto delete_rx;
 	if (!ASSERT_OK(init_iface(ifobj_tx, worker_testapp_validate_tx), "init TX"))
diff --git a/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c b/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
index 683306db8594..023d8befd4ca 100644
--- a/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
+++ b/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
@@ -26,8 +26,10 @@ SEC("xdp.frags") int xsk_def_prog(struct xdp_md *xdp)
 
 SEC("xdp.frags") int xsk_xdp_drop(struct xdp_md *xdp)
 {
+	static unsigned int drop_idx;
+
 	/* Drop every other packet */
-	if (idx++ % 2)
+	if (drop_idx++ % 2)
 		return XDP_DROP;
 
 	return bpf_redirect_map(&xsk, 0, XDP_DROP);
diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
index 05b3cebc5ca9..7dad8556a722 100644
--- a/tools/testing/selftests/bpf/xskxceiver.c
+++ b/tools/testing/selftests/bpf/xskxceiver.c
@@ -80,6 +80,7 @@
 #include <linux/mman.h>
 #include <linux/netdev.h>
 #include <linux/ethtool.h>
+#include <linux/align.h>
 #include <arpa/inet.h>
 #include <net/if.h>
 #include <locale.h>
@@ -333,6 +334,7 @@ static void print_tests(void)
 int main(int argc, char **argv)
 {
 	const size_t total_tests = ARRAY_SIZE(tests) + ARRAY_SIZE(ci_skip_tests);
+	u32 cache_line_size, max_frags, umem_tailroom;
 	struct pkt_stream *rx_pkt_stream_default;
 	struct pkt_stream *tx_pkt_stream_default;
 	struct ifobject *ifobj_tx, *ifobj_rx;
@@ -354,6 +356,27 @@ int main(int argc, char **argv)
 
 	setlocale(LC_ALL, "");
 
+	cache_line_size = read_procfs_val(SMP_CACHE_BYTES_PATH);
+	if (!cache_line_size) {
+		ksft_print_msg("Can't get SMP_CACHE_BYTES from system, using default (64)\n");
+		cache_line_size = 64;
+	}
+
+	max_frags = read_procfs_val(MAX_SKB_FRAGS_PATH);
+	if (!max_frags) {
+		ksft_print_msg("Can't get MAX_SKB_FRAGS from system, using default (17)\n");
+		max_frags = 17;
+	}
+	ifobj_tx->max_skb_frags = max_frags;
+	ifobj_rx->max_skb_frags = max_frags;
+
+	/* 48 bytes is a part of skb_shared_info w/o frags array;
+	 * 16 bytes is sizeof(skb_frag_t)
+	 */
+	umem_tailroom = ALIGN(48 + (max_frags * 16), cache_line_size);
+	ifobj_tx->umem_tailroom = umem_tailroom;
+	ifobj_rx->umem_tailroom = umem_tailroom;
+
 	parse_command_line(ifobj_tx, ifobj_rx, argc, argv);
 
 	if (opt_print_tests) {