Add UBLK_F_SUPPORT_RQ_AFFINITY to kublk's feature table and a
--rq_affinity flag to request it at ADD_DEV time, and add
test_generic_18.sh: writes and verifies data on a loop device with
I/O pinned to one CPU while cycling rq_affinity through 0, 1 and 2.
Skipped on kernels without UBLK_F_SUPPORT_RQ_AFFINITY.

Signed-off-by: Yoav Cohen <yoav@nvidia.com>
---
 tools/testing/selftests/ublk/Makefile         |  1 +
 tools/testing/selftests/ublk/kublk.c          |  6 ++-
 .../testing/selftests/ublk/test_generic_18.sh | 42 +++++++++++++++++++
 3 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/ublk/test_generic_18.sh

diff --git a/tools/testing/selftests/ublk/Makefile b/tools/testing/selftests/ublk/Makefile
index 37883e9d50ec..d12e9879b89a 100644
--- a/tools/testing/selftests/ublk/Makefile
+++ b/tools/testing/selftests/ublk/Makefile
@@ -19,6 +19,7 @@ TEST_PROGS += test_generic_12.sh
 TEST_PROGS += test_generic_13.sh
 TEST_PROGS += test_generic_16.sh
 TEST_PROGS += test_generic_17.sh
+TEST_PROGS += test_generic_18.sh
 
 TEST_PROGS += test_batch_01.sh
 TEST_PROGS += test_batch_02.sh
diff --git a/tools/testing/selftests/ublk/kublk.c b/tools/testing/selftests/ublk/kublk.c
index 2400b4615766..e3afef0e7628 100644
--- a/tools/testing/selftests/ublk/kublk.c
+++ b/tools/testing/selftests/ublk/kublk.c
@@ -2083,6 +2083,7 @@ static int cmd_dev_get_features(void)
 		FEAT_NAME(UBLK_F_NO_AUTO_PART_SCAN),
 		FEAT_NAME(UBLK_F_SHMEM_ZC),
 		FEAT_NAME(UBLK_F_IO_DESC_SIZE),
+		FEAT_NAME(UBLK_F_SUPPORT_RQ_AFFINITY),
 	};
 	struct ublk_dev *dev;
 	__u64 features = 0;
@@ -2180,7 +2181,7 @@ static void __cmd_create_help(char *exe, bool recovery)
 	printf("\t[--nthreads threads] [--per_io_tasks]\n");
 	printf("\t[--integrity_capable] [--integrity_reftag] [--metadata_size SIZE] "
 		 "[--pi_offset OFFSET] [--csum_type ip|t10dif|nvme] [--tag_size SIZE]\n");
-	printf("\t[--batch|-b] [--rotate_auto_buf] [--no_auto_part_scan]\n");
+	printf("\t[--batch|-b] [--rotate_auto_buf] [--no_auto_part_scan] [--rq_affinity]\n");
 	printf("\t[--io_desc_size SIZE]\n");
 	printf("\t[target options] [backfile1] [backfile2] ...\n");
 	printf("\tdefault: nr_queues=2(max 32), depth=128(max 1024), dev_id=-1(auto allocation)\n");
@@ -2260,6 +2261,7 @@ int main(int argc, char *argv[])
 		{ "batch",              0,      NULL, 'b'},
 		{ "rotate_auto_buf",	0,	NULL,  0 },
 		{ "no_auto_part_scan",	0,	NULL,  0 },
+		{ "rq_affinity",	0,	NULL,  0 },
 		{ "shmem_zc",		0,	NULL,  0  },
 		{ "htlb",		1,	NULL,  0  },
 		{ "rdonly_shmem_buf",	0,	NULL,  0  },
@@ -2407,6 +2409,8 @@ int main(int argc, char *argv[])
 				ctx.safe_stop = 1;
 			if (!strcmp(longopts[option_idx].name, "no_auto_part_scan"))
 				ctx.flags |= UBLK_F_NO_AUTO_PART_SCAN;
+			if (!strcmp(longopts[option_idx].name, "rq_affinity"))
+				ctx.flags |= UBLK_F_SUPPORT_RQ_AFFINITY;
 			if (!strcmp(longopts[option_idx].name, "shmem_zc"))
 				ctx.flags |= UBLK_F_SHMEM_ZC;
 			if (!strcmp(longopts[option_idx].name, "htlb"))
diff --git a/tools/testing/selftests/ublk/test_generic_18.sh b/tools/testing/selftests/ublk/test_generic_18.sh
new file mode 100755
index 000000000000..c899a5bf0364
--- /dev/null
+++ b/tools/testing/selftests/ublk/test_generic_18.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+. "$(cd "$(dirname "$0")" && pwd)"/test_common.sh
+
+ERR_CODE=0
+
+if ! _have_program fio; then
+	exit "$UBLK_SKIP_CODE"
+fi
+
+if ! _have_feature "SUPPORT_RQ_AFFINITY"; then
+	exit "$UBLK_SKIP_CODE"
+fi
+
+_prep_test "loop" "write and verify I/O across rq_affinity settings"
+
+_create_backfile 0 256M
+
+dev_id=$(_add_ublk_dev -t loop --rq_affinity "${UBLK_BACKFILES[0]}")
+_check_add_dev $TID $?
+
+rq_affinity_path=/sys/block/ublkb"${dev_id}"/queue/rq_affinity
+
+for affinity in 0 1 2; do
+	echo "${affinity}" > "${rq_affinity_path}"
+
+	# Pin submission to a single CPU so rq_affinity has somewhere to
+	# redirect completion to.
+	taskset -c 0 fio --name=verify --rw=randwrite --direct=1 \
+		--ioengine=libaio --bs=8k --iodepth=32 --verify=crc32c \
+		--do_verify=1 --verify_state_save=0 \
+		--filename=/dev/ublkb"${dev_id}" --size=256M > /dev/null
+	if [ $? -ne 0 ]; then
+		echo "fio verify failed with rq_affinity=${affinity}"
+		ERR_CODE=255
+		break
+	fi
+done
+
+_cleanup_test
+_show_result $TID $ERR_CODE
-- 
2.50.1 (Apple Git-155)