io_uring: implement IORING_REGISTER_IOWQ_MAX_WORKERS op decoding

Introduced by Linux commit v5.15-rc1~83^2~22.

* src/xlat/uring_iowq_acct.in: New file.
* src/io_uring.c: Include "xlat/uring_iowq_acct.h".
(print_io_uring_iowq_acct): New function.
(SYS_FUNC(io_uring_register)) <case IORING_REGISTER_IOWQ_MAX_WORKERS>:
Decode, call print_io_uring_iowq_acct.
* src/xlat/uring_register_opcodes.in (IORING_REGISTER_IOWQ_MAX_WORKERS):
New constant.
* tests/io_uring_register.c: Update expected output, add
IORING_REGISTER_IOWQ_MAX_WORKERS checks.

4 files changed, 76 insertions, 2 deletions

diff --git a/src/io_uring.c b/src/io_uring.c
index 39f91d5f0..796e374bc 100644
--- a/src/io_uring.c
+++ b/src/io_uring.c
@@ -12,6 +12,7 @@
 
 #include "xlat/uring_enter_flags.h"
 #include "xlat/uring_files_update_fds.h"
+#include "xlat/uring_iowq_acct.h"
 #include "xlat/uring_op_flags.h"
 #include "xlat/uring_ops.h"
 #include "xlat/uring_setup_features.h"
@@ -471,6 +472,19 @@ print_io_uring_update_rsrc(struct tcb *tcp, const kernel_ulong_t addr,
 	tprint_struct_end();
 }
 
+static int
+print_io_uring_iowq_acct(struct tcb *tcp, const kernel_ulong_t addr,
+		     const unsigned int nargs)
+{
+	uint32_t val;
+	bool ret = print_array_ex(tcp, addr, nargs, &val, sizeof(val),
+				  tfetch_mem, print_uint_array_member, NULL,
+				  PAF_PRINT_INDICES | XLAT_STYLE_FMT_U,
+				  uring_iowq_acct, "IO_WQ_???");
+
+	return ret ? 0 : RVAL_DECODED;
+}
+
 SYS_FUNC(io_uring_register)
 {
 	const int fd = tcp->u_arg[0];
@@ -522,6 +536,11 @@ SYS_FUNC(io_uring_register)
 	case IORING_REGISTER_IOWQ_AFF:
 		print_affinitylist(tcp, arg, nargs);
 		break;
+	case IORING_REGISTER_IOWQ_MAX_WORKERS:
+		rc = print_io_uring_iowq_acct(tcp, arg, nargs);
+		if (entering(tcp) && !rc)
+			tprint_value_changed();
+		break;
 	case IORING_UNREGISTER_BUFFERS:
 	case IORING_UNREGISTER_FILES:
 	case IORING_UNREGISTER_EVENTFD:
diff --git a/src/xlat/uring_iowq_acct.in b/src/xlat/uring_iowq_acct.in
new file mode 100644
index 000000000..136057835
--- /dev/null
+++ b/src/xlat/uring_iowq_acct.in
@@ -0,0 +1,3 @@
+#value_indexed
+IO_WQ_BOUND	0
+IO_WQ_UNBOUND	1
diff --git a/src/xlat/uring_register_opcodes.in b/src/xlat/uring_register_opcodes.in
index daa932dcd..966d8cb37 100644
--- a/src/xlat/uring_register_opcodes.in
+++ b/src/xlat/uring_register_opcodes.in
@@ -19,3 +19,4 @@ IORING_REGISTER_BUFFERS2
 IORING_REGISTER_BUFFERS_UPDATE
 IORING_REGISTER_IOWQ_AFF
 IORING_UNREGISTER_IOWQ_AFF
+IORING_REGISTER_IOWQ_MAX_WORKERS
diff --git a/tests/io_uring_register.c b/tests/io_uring_register.c
index 392804f31..f329c8095 100644
--- a/tests/io_uring_register.c
+++ b/tests/io_uring_register.c
@@ -165,7 +165,7 @@ main(void)
 
 
 	/* Invalid op */
-	static const unsigned int invalid_ops[] = { 0xbadc0dedU, 19 };
+	static const unsigned int invalid_ops[] = { 0xbadc0dedU, 20 };
 
 	for (size_t i = 0; i < ARRAY_SIZE(invalid_ops); i++) {
 		sys_io_uring_register(fd_null, invalid_ops[i], path_null,
@@ -455,7 +455,7 @@ main(void)
 		  "register_op=", ARG_STR(IORING_UNREGISTER_IOWQ_AFF),
 		  true },
 		{ ARG_STR(IORING_RESTRICTION_REGISTER_OP), true,
-		  "register_op=", 19, " /* IORING_REGISTER_??? */", false },
+		  "register_op=", 20, " /* IORING_REGISTER_??? */", false },
 		{ ARG_STR(IORING_RESTRICTION_REGISTER_OP), true,
 		  "register_op=", 255, " /* IORING_REGISTER_??? */", false },
 		{ ARG_STR(IORING_RESTRICTION_SQE_OP), true,
@@ -910,6 +910,57 @@ main(void)
 	       "], %zu) = %s\n",
 	       fd_null, path_null, sizeof(aff), errstr);
 
+
+	/* IORING_REGISTER_IOWQ_MAX_WORKERS */
+	unsigned int maxw[] = { 0, 1, 0xbedfaced };
+	const unsigned int *arg_maxw = tail_memdup(maxw, sizeof(maxw));
+	const unsigned int *arg_maxw_end = arg_maxw + ARRAY_SIZE(maxw);
+
+	sys_io_uring_register(fd_null, 19, NULL, 0xfacefeed);
+	printf("io_uring_register(%u<%s>, "
+	       XLAT_KNOWN(0x13, "IORING_REGISTER_IOWQ_MAX_WORKERS")
+	       ", NULL, 4207869677) = %s\n",
+	       fd_null, path_null, errstr);
+
+	sys_io_uring_register(fd_null, 19, arg_maxw_end, 0);
+	printf("io_uring_register(%u<%s>, "
+	       XLAT_KNOWN(0x13, "IORING_REGISTER_IOWQ_MAX_WORKERS")
+	       ", [], 0) = %s\n",
+	       fd_null, path_null, errstr);
+
+	sys_io_uring_register(fd_null, 19, arg_maxw_end, 1);
+	printf("io_uring_register(%u<%s>, "
+	       XLAT_KNOWN(0x13, "IORING_REGISTER_IOWQ_MAX_WORKERS")
+	       ", %p, 1) = %s\n",
+	       fd_null, path_null, arg_maxw_end, errstr);
+
+	sys_io_uring_register(fd_null, 19, arg_maxw_end - 1, 2);
+	printf("io_uring_register(%u<%s>, "
+	       XLAT_KNOWN(0x13, "IORING_REGISTER_IOWQ_MAX_WORKERS") ", [["
+	       XLAT_KNOWN(0, "IO_WQ_BOUND") "] = 3202329837, ... /* %p */]"
+	       ", 2) = %s\n",
+	       fd_null, path_null, arg_maxw_end, errstr);
+
+	sys_io_uring_register(fd_null, 19, arg_maxw, 3);
+	printf("io_uring_register(%u<%s>, "
+	       XLAT_KNOWN(0x13, "IORING_REGISTER_IOWQ_MAX_WORKERS") ", "
+	       "[[" XLAT_KNOWN(0, "IO_WQ_BOUND") "] = 0, ["
+	       XLAT_KNOWN(1, "IO_WQ_UNBOUND") "] = 1, ["
+	       XLAT_UNKNOWN(2, "IO_WQ_???") "] = 3202329837] => "
+#if RETVAL_INJECTED
+	       "[[" XLAT_KNOWN(0, "IO_WQ_BOUND") "] = 0, ["
+	       XLAT_KNOWN(1, "IO_WQ_UNBOUND") "] = 1, ["
+	       XLAT_UNKNOWN(2, "IO_WQ_???") "] = 3202329837]"
+#else
+	       "%p"
+#endif
+	       ", 3) = %s\n",
+	       fd_null, path_null,
+#if !RETVAL_INJECTED
+	       arg_maxw,
+#endif
+	       errstr);
+
 	puts("+++ exited with 0 +++");
 	return 0;
 }