diff mbox series

[v2,3/4] kselftest/arm64: Add tests for SVE vector configuration

Message ID 20210728163318.51492-4-broonie@kernel.org
State Superseded
Headers show
Series kselftest/arm64: Vector length configuration tests | expand

Commit Message

Mark Brown July 28, 2021, 4:33 p.m. UTC
We provide interfaces for configuring the SVE vector length seen by
processes using prctl and also via /proc for configuring the default
values. Provide tests that exercise all these interfaces and verify that
they take effect as expected, though at present no test fully enumerates
all the possible vector lengths.

A subset of this is already tested via sve-probe-vls but the /proc
interfaces are not currently covered at all.

In preparation for the forthcoming support for SME, the Scalable Matrix
Extension, which has separately but similarly configured vector lengths
which we expect to offer similar userspace interfaces for, all the actual
files and prctls used are parameterised and we don't validate that the
architectural minimum vector length is the minimum we see.

Signed-off-by: Mark Brown <broonie@kernel.org>

---
 tools/testing/selftests/arm64/fp/.gitignore   |   1 +
 tools/testing/selftests/arm64/fp/Makefile     |   3 +-
 tools/testing/selftests/arm64/fp/vec-syscfg.c | 580 ++++++++++++++++++
 3 files changed, 583 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/arm64/fp/vec-syscfg.c

-- 
2.20.1

Comments

Dave Martin July 29, 2021, 9:52 a.m. UTC | #1
On Wed, Jul 28, 2021 at 05:33:17PM +0100, Mark Brown wrote:
> We provide interfaces for configuring the SVE vector length seen by

> processes using prctl and also via /proc for configuring the default

> values. Provide tests that exercise all these interfaces and verify that

> they take effect as expected, though at present no test fully enumerates

> all the possible vector lengths.

> 

> A subset of this is already tested via sve-probe-vls but the /proc

> interfaces are not currently covered at all.

> 

> In preparation for the forthcoming support for SME, the Scalable Matrix

> Extension, which has separately but similarly configured vector lengths

> which we expect to offer similar userspace interfaces for, all the actual

> files and prctls used are parameterised and we don't validate that the

> architectural minimum vector length is the minimum we see.

> 

> Signed-off-by: Mark Brown <broonie@kernel.org>

> ---

>  tools/testing/selftests/arm64/fp/.gitignore   |   1 +

>  tools/testing/selftests/arm64/fp/Makefile     |   3 +-

>  tools/testing/selftests/arm64/fp/vec-syscfg.c | 580 ++++++++++++++++++

>  3 files changed, 583 insertions(+), 1 deletion(-)

>  create mode 100644 tools/testing/selftests/arm64/fp/vec-syscfg.c

> 

> diff --git a/tools/testing/selftests/arm64/fp/.gitignore b/tools/testing/selftests/arm64/fp/.gitignore

> index 6b53a7b60fee..b67395903b9b 100644

> --- a/tools/testing/selftests/arm64/fp/.gitignore

> +++ b/tools/testing/selftests/arm64/fp/.gitignore

> @@ -3,4 +3,5 @@ rdvl-sve

>  sve-probe-vls

>  sve-ptrace

>  sve-test

> +vec-syscfg

>  vlset

> diff --git a/tools/testing/selftests/arm64/fp/Makefile b/tools/testing/selftests/arm64/fp/Makefile

> index fa3a0167db2d..f2abdd6ba12e 100644

> --- a/tools/testing/selftests/arm64/fp/Makefile

> +++ b/tools/testing/selftests/arm64/fp/Makefile

> @@ -1,7 +1,7 @@

>  # SPDX-License-Identifier: GPL-2.0

>  

>  CFLAGS += -I../../../../../usr/include/

> -TEST_GEN_PROGS := sve-ptrace sve-probe-vls

> +TEST_GEN_PROGS := sve-ptrace sve-probe-vls vec-syscfg

>  TEST_PROGS_EXTENDED := fpsimd-test fpsimd-stress \

>  	rdvl-sve \

>  	sve-test sve-stress \

> @@ -16,6 +16,7 @@ sve-ptrace: sve-ptrace.o sve-ptrace-asm.o

>  sve-probe-vls: sve-probe-vls.o rdvl.o

>  sve-test: sve-test.o

>  	$(CC) -nostdlib $^ -o $@

> +vec-syscfg: vec-syscfg.o rdvl.o

>  vlset: vlset.o

>  

>  include ../../lib.mk

> diff --git a/tools/testing/selftests/arm64/fp/vec-syscfg.c b/tools/testing/selftests/arm64/fp/vec-syscfg.c

> new file mode 100644

> index 000000000000..63d080537d21

> --- /dev/null

> +++ b/tools/testing/selftests/arm64/fp/vec-syscfg.c

> @@ -0,0 +1,580 @@

> +// SPDX-License-Identifier: GPL-2.0-only

> +/*

> + * Copyright (C) 2021 ARM Limited.

> + * Original author: Mark Brown <broonie@kernel.org>

> + */

> +#include <errno.h>

> +#include <fcntl.h>

> +#include <stddef.h>

> +#include <stdio.h>

> +#include <stdlib.h>

> +#include <string.h>

> +#include <unistd.h>

> +#include <sys/auxv.h>

> +#include <sys/prctl.h>

> +#include <sys/ptrace.h>


Nit: ^ also still not used? (I think you caught <asm/ptrace.h> already.)

(Hmm, there must be a tool for weeding #includes somewhere...)

> +#include <sys/types.h>

> +#include <sys/wait.h>

> +#include <asm/sigcontext.h>

> +#include <asm/hwcap.h>

> +

> +#include "../../kselftest.h"

> +#include "rdvl.h"

> +

> +#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

> +

> +#define ARCH_MIN_VL SVE_VL_MIN

> +

> +struct vec_data {

> +	const char *name;

> +	unsigned long hwcap_type;

> +	unsigned long hwcap;

> +	const char *rdvl_binary;

> +	int (*rdvl)(void);

> +

> +	int prctl_get;

> +	int prctl_set;

> +	const char *default_vl_file;

> +

> +	int default_vl;

> +	int min_vl;

> +	int max_vl;

> +};

> +

> +

> +static struct vec_data vec_data[] = {

> +	{

> +		.name = "SVE",

> +		.hwcap_type = AT_HWCAP,

> +		.hwcap = HWCAP_SVE,

> +		.rdvl = rdvl_sve,

> +		.rdvl_binary = "./rdvl-sve",

> +		.prctl_get = PR_SVE_GET_VL,

> +		.prctl_set = PR_SVE_SET_VL,

> +		.default_vl_file = "/proc/sys/abi/sve_default_vector_length",

> +	},

> +};

> +

> +/* Start a new process and return the vector length it sees */

> +int get_child_rdvl(struct vec_data *data)

> +{

> +	FILE *out;

> +	int pipefd[2];

> +	pid_t pid, child;

> +	int read_vl, ret;

> +

> +	ret = pipe(pipefd);

> +	if (ret == -1) {

> +		ksft_print_msg("pipe() failed: %d (%s)\n",

> +			       errno, strerror(errno));

> +		return -1;

> +	}

> +

> +	fflush(stdout);

> +

> +	child = fork();

> +	if (child == -1) {

> +		ksft_print_msg("fork() failed: %d (%s)\n",

> +			       errno, strerror(errno));

> +		return -1;


Leaks pipefd[0], pipefd[1]?

> +	}

> +

> +	/* Child: put vector length on the pipe */

> +	if (child == 0) {

> +		/*

> +		 * Replace stdout with the pipe, errors to stderr from

> +		 * here as kselftest prints to stdout.

> +		 */

> +		ret = dup2(pipefd[1], 1);

> +		if (ret == -1) {

> +			fprintf(stderr, "dup2() %d\n", errno);

> +			exit(EXIT_FAILURE);

> +		}

> +

> +		/* exec() a new binary which puts the VL on stdout */

> +		ret = execl(data->rdvl_binary, data->rdvl_binary, NULL);

> +		fprintf(stderr, "execl(%s) failed: %d\n",

> +			data->rdvl_binary, errno, strerror(errno));

> +

> +		exit(EXIT_FAILURE);

> +	}

> +

> +	close(pipefd[1]);

> +

> +	/* Parent; wait for the exit status from the child & verify it */

> +	while (1) {

> +		pid = wait(&ret);

> +		if (pid == -1) {

> +			ksft_print_msg("wait() failed: %d (%s)\n",

> +				       errno, strerror(errno));

> +			return -1;


Leaks pipefd[0]?

> +		}

> +

> +		if (pid != child)

> +			continue;

> +

> +		if (!WIFEXITED(ret)) {

> +			ksft_print_msg("child exited abnormally\n");

> +			return -1;


Same from here up to the fclose().


Although this looks like it might have been based on code I wrote
previously(?), I guess it might be better to move all the
post-child-exit code out of the loop, since it really only executes
once, and any mishap is treated as fatal anyway.  It looks kind of
weird to have close() in the loop (even if hidden now in fclose())
with pipe() outside.

There's only one child anyway, and we treat !WIFEXITED() as an error
(without WUNTRACED or similar and since we are not a tracer,
WIFSIGNALED is the only other possbility IIUC.)

> +		}

> +

> +		if (WEXITSTATUS(ret) != 0) {

> +			ksft_print_msg("child returned error %d\n",

> +				       WEXITSTATUS(ret));

> +			return -1;

> +		}

> +

> +		out = fdopen(pipefd[0], "r");

> +		if (!out) {

> +			ksft_print_msg("failed to open child stdout\n");

> +			return -1;

> +		}

> +

> +		ret = fscanf(out, "%d", &read_vl);


Is it still worth slurping the newline here?  That's the only way to
tell the difference between complete line and truncation of the stream.

The "%d%*1[\n]*n" trick from my previous reply would probably work for
that.  Or maybe just checking for the '\n' with an fgetc() after the
fscanf() would work.  I don't remember offhand whether scanf is allowed
to silently consume trailing whitespace after a conversion, which would
be a problem for the fgetc() approach.  Maybe not though.

OTOH this is a pipe, and with my suggestion on the sve-rdvl patch,
the child should report nonzero exit status if something goes wrong on
its end.  So there's not a lot that can actually go wrong that we
wouldn't detect somehow.

Either way, this still looks a lot like file_read_integer() and the
error detection discussion applies to both.

Could the code be factored out as

int ffile_read_integer(int *val, FILE *f) {
	...
}

int file_read_integer(const char *name, int val) {
	fopen() ... ffile_read_integer() ... fclose()
}

> +		fclose(out);

> +		if (ret != 1) {

> +			ksft_print_msg("failed to parse VL from '%s'\n",

> +				       data->rdvl_binary);

> +			return -1;

> +		}

> +

> +		return read_vl;

> +	}

> +}

> +

> +int file_read_integer(const char *name, int *val)

> +{

> +	FILE *f;

> +	int ret;

> +

> +	f = fopen(name, "r");

> +	if (!f) {

> +		ksft_test_result_fail("Unable to open %s: %d (%s)\n",

> +				      name, errno,

> +				      strerror(errno));

> +		return -1;

> +	}

> +

> +	ret = fscanf(f, "%d", val);

> +	fclose(f);

> +	if (ret != 1) {

> +		ksft_test_result_fail("Failed to parse %s\n", name);

> +		return -1;

> +	}

> +

> +	return 0;

> +}


[...]

> +typedef void (*test_type)(struct vec_data *);

> +

> +test_type tests[] = {

> +	/*

> +	 * The default/min/max tests must be first and in this order

> +	 * to provide data for other tests.

> +	 */

> +	proc_read_default,

> +	proc_write_min,

> +	proc_write_max,

> +

> +	prctl_get,

> +	prctl_set,

> +	prctl_set_no_child,

> +	prctl_set_for_child,

> +	prctl_set_onexec,

> +};


This can be static const too come to think of it, and every function
except main() can be static...

[...]

> +int main(void)

> +{

> +	int i, j;

> +

> +	ksft_print_header();

> +	ksft_set_plan(ARRAY_SIZE(tests) * ARRAY_SIZE(vec_data));

> +

> +	for (i = 0; i < ARRAY_SIZE(vec_data); i++) {

> +		struct vec_data *data = &vec_data[i];

> +		int supported = getauxval(data->hwcap_type) & data->hwcap;

> +

> +		for (j = 0; j < ARRAY_SIZE(tests); j++) {

> +			if (supported)


Did we commit to never defining hwcaps beyond bit 31?  It sort of looks
this way from arch/arm64/include/uapi/asm/hwcap.h, but I can't remember
the reason.  I'd say something to do with compat, only of course that
has its own hwcaps.

Since getauxval() returns an unsigned long, would it be a good idea to
make this:

		int supported = (getauxval(data->hwcap_type) & data->hwcap) != 0;

or

		unsigned long supported_hwcaps = getauxval(data->hwcap_type);

		/* ... */

			if (supported_hwcaps & data->hwcap)

just to avoid future surprises?

[...]

Cheers
---Dave
diff mbox series

Patch

diff --git a/tools/testing/selftests/arm64/fp/.gitignore b/tools/testing/selftests/arm64/fp/.gitignore
index 6b53a7b60fee..b67395903b9b 100644
--- a/tools/testing/selftests/arm64/fp/.gitignore
+++ b/tools/testing/selftests/arm64/fp/.gitignore
@@ -3,4 +3,5 @@  rdvl-sve
 sve-probe-vls
 sve-ptrace
 sve-test
+vec-syscfg
 vlset
diff --git a/tools/testing/selftests/arm64/fp/Makefile b/tools/testing/selftests/arm64/fp/Makefile
index fa3a0167db2d..f2abdd6ba12e 100644
--- a/tools/testing/selftests/arm64/fp/Makefile
+++ b/tools/testing/selftests/arm64/fp/Makefile
@@ -1,7 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0
 
 CFLAGS += -I../../../../../usr/include/
-TEST_GEN_PROGS := sve-ptrace sve-probe-vls
+TEST_GEN_PROGS := sve-ptrace sve-probe-vls vec-syscfg
 TEST_PROGS_EXTENDED := fpsimd-test fpsimd-stress \
 	rdvl-sve \
 	sve-test sve-stress \
@@ -16,6 +16,7 @@  sve-ptrace: sve-ptrace.o sve-ptrace-asm.o
 sve-probe-vls: sve-probe-vls.o rdvl.o
 sve-test: sve-test.o
 	$(CC) -nostdlib $^ -o $@
+vec-syscfg: vec-syscfg.o rdvl.o
 vlset: vlset.o
 
 include ../../lib.mk
diff --git a/tools/testing/selftests/arm64/fp/vec-syscfg.c b/tools/testing/selftests/arm64/fp/vec-syscfg.c
new file mode 100644
index 000000000000..63d080537d21
--- /dev/null
+++ b/tools/testing/selftests/arm64/fp/vec-syscfg.c
@@ -0,0 +1,580 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 ARM Limited.
+ * Original author: Mark Brown <broonie@kernel.org>
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/auxv.h>
+#include <sys/prctl.h>
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <asm/sigcontext.h>
+#include <asm/hwcap.h>
+
+#include "../../kselftest.h"
+#include "rdvl.h"
+
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
+
+#define ARCH_MIN_VL SVE_VL_MIN
+
+struct vec_data {
+	const char *name;
+	unsigned long hwcap_type;
+	unsigned long hwcap;
+	const char *rdvl_binary;
+	int (*rdvl)(void);
+
+	int prctl_get;
+	int prctl_set;
+	const char *default_vl_file;
+
+	int default_vl;
+	int min_vl;
+	int max_vl;
+};
+
+
+static struct vec_data vec_data[] = {
+	{
+		.name = "SVE",
+		.hwcap_type = AT_HWCAP,
+		.hwcap = HWCAP_SVE,
+		.rdvl = rdvl_sve,
+		.rdvl_binary = "./rdvl-sve",
+		.prctl_get = PR_SVE_GET_VL,
+		.prctl_set = PR_SVE_SET_VL,
+		.default_vl_file = "/proc/sys/abi/sve_default_vector_length",
+	},
+};
+
+/* Start a new process and return the vector length it sees */
+int get_child_rdvl(struct vec_data *data)
+{
+	FILE *out;
+	int pipefd[2];
+	pid_t pid, child;
+	int read_vl, ret;
+
+	ret = pipe(pipefd);
+	if (ret == -1) {
+		ksft_print_msg("pipe() failed: %d (%s)\n",
+			       errno, strerror(errno));
+		return -1;
+	}
+
+	fflush(stdout);
+
+	child = fork();
+	if (child == -1) {
+		ksft_print_msg("fork() failed: %d (%s)\n",
+			       errno, strerror(errno));
+		return -1;
+	}
+
+	/* Child: put vector length on the pipe */
+	if (child == 0) {
+		/*
+		 * Replace stdout with the pipe, errors to stderr from
+		 * here as kselftest prints to stdout.
+		 */
+		ret = dup2(pipefd[1], 1);
+		if (ret == -1) {
+			fprintf(stderr, "dup2() %d\n", errno);
+			exit(EXIT_FAILURE);
+		}
+
+		/* exec() a new binary which puts the VL on stdout */
+		ret = execl(data->rdvl_binary, data->rdvl_binary, NULL);
+		fprintf(stderr, "execl(%s) failed: %d\n",
+			data->rdvl_binary, errno, strerror(errno));
+
+		exit(EXIT_FAILURE);
+	}
+
+	close(pipefd[1]);
+
+	/* Parent; wait for the exit status from the child & verify it */
+	while (1) {
+		pid = wait(&ret);
+		if (pid == -1) {
+			ksft_print_msg("wait() failed: %d (%s)\n",
+				       errno, strerror(errno));
+			return -1;
+		}
+
+		if (pid != child)
+			continue;
+
+		if (!WIFEXITED(ret)) {
+			ksft_print_msg("child exited abnormally\n");
+			return -1;
+		}
+
+		if (WEXITSTATUS(ret) != 0) {
+			ksft_print_msg("child returned error %d\n",
+				       WEXITSTATUS(ret));
+			return -1;
+		}
+
+		out = fdopen(pipefd[0], "r");
+		if (!out) {
+			ksft_print_msg("failed to open child stdout\n");
+			return -1;
+		}
+
+		ret = fscanf(out, "%d", &read_vl);
+		fclose(out);
+		if (ret != 1) {
+			ksft_print_msg("failed to parse VL from '%s'\n",
+				       data->rdvl_binary);
+			return -1;
+		}
+
+		return read_vl;
+	}
+}
+
+int file_read_integer(const char *name, int *val)
+{
+	FILE *f;
+	int ret;
+
+	f = fopen(name, "r");
+	if (!f) {
+		ksft_test_result_fail("Unable to open %s: %d (%s)\n",
+				      name, errno,
+				      strerror(errno));
+		return -1;
+	}
+
+	ret = fscanf(f, "%d", val);
+	fclose(f);
+	if (ret != 1) {
+		ksft_test_result_fail("Failed to parse %s\n", name);
+		return -1;
+	}
+
+	return 0;
+}
+
+int file_write_integer(const char *name, int val)
+{
+	FILE *f;
+	int ret;
+
+	f = fopen(name, "w");
+	if (!f) {
+		ksft_test_result_fail("Unable to open %s: %d (%s)\n",
+				      name, errno,
+				      strerror(errno));
+		return -1;
+	}
+
+	fprintf(f, "%d", val);
+	fclose(f);
+	if (ret < 0) {
+		ksft_test_result_fail("Error writing %d to %s\n",
+				      val, name);
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * Verify that we can read the default VL via proc, checking that it
+ * is set in a freshly spawned child.
+ */
+void proc_read_default(struct vec_data *data)
+{
+	int default_vl, child_vl, ret;
+
+	ret = file_read_integer(data->default_vl_file, &default_vl);
+	if (ret != 0)
+		return;
+
+	/* Is this the actual default seen by new processes? */
+	child_vl = get_child_rdvl(data);
+	if (child_vl != default_vl) {
+		ksft_test_result_fail("%s is %d but child VL is %d\n",
+				      data->default_vl_file,
+				      default_vl, child_vl);
+		return;
+	}
+
+	ksft_test_result_pass("%s default vector length %d\n", data->name,
+			      default_vl);
+	data->default_vl = default_vl;
+}
+
+/* Verify that we can write a minimum value and have it take effect */
+void proc_write_min(struct vec_data *data)
+{
+	int ret, new_default, child_vl;
+
+	if (geteuid() != 0) {
+		ksft_test_result_skip("Need to be root to write to /proc\n");
+		return;
+	}
+
+	ret = file_write_integer(data->default_vl_file, ARCH_MIN_VL);
+	if (ret != 0)
+		return;
+
+	/* What was the new value? */
+	ret = file_read_integer(data->default_vl_file, &new_default);
+	if (ret != 0)
+		return;
+
+	/* Did it take effect in a new process? */
+	child_vl = get_child_rdvl(data);
+	if (child_vl != new_default) {
+		ksft_test_result_fail("%s is %d but child VL is %d\n",
+				      data->default_vl_file,
+				      new_default, child_vl);
+		return;
+	}
+
+	ksft_test_result_pass("%s minimum vector length %d\n", data->name,
+			      new_default);
+	data->min_vl = new_default;
+
+	file_write_integer(data->default_vl_file, data->default_vl);
+}
+
+/* Verify that we can write a maximum value and have it take effect */
+void proc_write_max(struct vec_data *data)
+{
+	int ret, new_default, child_vl;
+
+	if (geteuid() != 0) {
+		ksft_test_result_skip("Need to be root to write to /proc\n");
+		return;
+	}
+
+	/* -1 is accepted by the /proc interface as the maximum VL */
+	ret = file_write_integer(data->default_vl_file, -1);
+	if (ret != 0)
+		return;
+
+	/* What was the new value? */
+	ret = file_read_integer(data->default_vl_file, &new_default);
+	if (ret != 0)
+		return;
+
+	/* Did it take effect in a new process? */
+	child_vl = get_child_rdvl(data);
+	if (child_vl != new_default) {
+		ksft_test_result_fail("%s is %d but child VL is %d\n",
+				      data->default_vl_file,
+				      new_default, child_vl);
+		return;
+	}
+
+	ksft_test_result_pass("%s maximum vector length %d\n", data->name,
+			      new_default);
+	data->max_vl = new_default;
+
+	file_write_integer(data->default_vl_file, data->default_vl);
+}
+
+/* Can we read back a VL from prctl? */
+void prctl_get(struct vec_data *data)
+{
+	int ret;
+
+	ret = prctl(data->prctl_get);
+	if (ret == -1) {
+		ksft_test_result_fail("%s prctl() read failed: %d (%s)\n",
+				      data->name, errno, strerror(errno));
+		return;
+	}
+
+	/* Mask out any flags */
+	ret &= PR_SVE_VL_LEN_MASK;
+
+	/* Is that what we can read back directly? */
+	if (ret == data->rdvl())
+		ksft_test_result_pass("%s current VL is %d\n",
+				      data->name, ret);
+	else
+		ksft_test_result_fail("%s prctl() VL %d but RDVL is %d\n",
+				      data->name, ret, data->rdvl());
+}
+
+/* Does the prctl let us set the VL we already have? */
+void prctl_set_same(struct vec_data *data)
+{
+	int cur_vl = data->rdvl();
+	int ret;
+
+	ret = prctl(data->prctl_set, cur_vl);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed: %d (%s)\n",
+				      data->name, errno, strerror(errno));
+		return;
+	}
+
+	if (cur_vl != data->rdvl())
+		ksft_test_result_pass("%s current VL is %d\n",
+				      data->name, ret);
+	else
+		ksft_test_result_fail("%s prctl() VL %d but RDVL is %d\n",
+				      data->name, ret, data->rdvl());
+}
+
+/* Can we set a new VL for this process? */
+void prctl_set(struct vec_data *data)
+{
+	int ret;
+
+	if (data->min_vl == data->max_vl) {
+		ksft_test_result_skip("%s only one VL supported\n",
+				      data->name);
+		return;
+	}
+
+	/* Try to set the minimum VL */
+	ret = prctl(data->prctl_set, data->min_vl);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed for %d: %d (%s)\n",
+				      data->name, data->min_vl,
+				      errno, strerror(errno));
+		return;
+	}
+
+	if ((ret & PR_SVE_VL_LEN_MASK) != data->min_vl) {
+		ksft_test_result_fail("%s prctl set %d but return value is %d\n",
+				      data->name, data->min_vl, data->rdvl());
+		return;
+	}
+
+	if (data->rdvl() != data->min_vl) {
+		ksft_test_result_fail("%s set %d but RDVL is %d\n",
+				      data->name, data->min_vl, data->rdvl());
+		return;
+	}
+
+	/* Try to set the maximum VL */
+	ret = prctl(data->prctl_set, data->max_vl);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed for %d: %d (%s)\n",
+				      data->name, data->max_vl,
+				      errno, strerror(errno));
+		return;
+	}
+
+	if ((ret & PR_SVE_VL_LEN_MASK) != data->max_vl) {
+		ksft_test_result_fail("%s prctl() set %d but return value is %d\n",
+				      data->name, data->max_vl, data->rdvl());
+		return;
+	}
+
+	/* The _INHERIT flag should not be present when we read the VL */
+	ret = prctl(data->prctl_get);
+	if (ret == -1) {
+		ksft_test_result_fail("%s prctl() read failed: %d (%s)\n",
+				      data->name, errno, strerror(errno));
+		return;
+	}
+
+	if (ret & PR_SVE_VL_INHERIT) {
+		ksft_test_result_fail("%s prctl() reports _INHERIT\n",
+				      data->name);
+		return;
+	}
+
+	ksft_test_result_pass("%s prctl() set min/max\n", data->name);
+}
+
+/* If we didn't request it a new VL shouldn't affect the child */
+void prctl_set_no_child(struct vec_data *data)
+{
+	int ret, child_vl;
+
+	if (data->min_vl == data->max_vl) {
+		ksft_test_result_skip("%s only one VL supported\n",
+				      data->name);
+		return;
+	}
+
+	ret = prctl(data->prctl_set, data->min_vl);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed for %d: %d (%s)\n",
+				      data->name, data->min_vl,
+				      errno, strerror(errno));
+		return;
+	}
+
+	/* Ensure the default VL is different */
+	ret = file_write_integer(data->default_vl_file, data->max_vl);
+	if (ret != 0)
+		return;
+
+	/* Check that the child has the default we just set */
+	child_vl = get_child_rdvl(data);
+	if (child_vl != data->max_vl) {
+		ksft_test_result_fail("%s is %d but child VL is %d\n",
+				      data->default_vl_file,
+				      data->max_vl, child_vl);
+		return;
+	}
+
+	ksft_test_result_pass("%s vector length used default\n", data->name);
+
+	file_write_integer(data->default_vl_file, data->default_vl);
+}
+
+/* If we didn't request it a new VL shouldn't affect the child */
+void prctl_set_for_child(struct vec_data *data)
+{
+	int ret, child_vl;
+
+	if (data->min_vl == data->max_vl) {
+		ksft_test_result_skip("%s only one VL supported\n",
+				      data->name);
+		return;
+	}
+
+	ret = prctl(data->prctl_set, data->min_vl | PR_SVE_VL_INHERIT);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed for %d: %d (%s)\n",
+				      data->name, data->min_vl,
+				      errno, strerror(errno));
+		return;
+	}
+
+	/* The _INHERIT flag should be present when we read the VL */
+	ret = prctl(data->prctl_get);
+	if (ret == -1) {
+		ksft_test_result_fail("%s prctl() read failed: %d (%s)\n",
+				      data->name, errno, strerror(errno));
+		return;
+	}
+	if (!(ret & PR_SVE_VL_INHERIT)) {
+		ksft_test_result_fail("%s prctl() does not report _INHERIT\n",
+				      data->name);
+		return;
+	}
+
+	/* Ensure the default VL is different */
+	ret = file_write_integer(data->default_vl_file, data->max_vl);
+	if (ret != 0)
+		return;
+
+	/* Check that the child inherited our VL */
+	child_vl = get_child_rdvl(data);
+	if (child_vl != data->min_vl) {
+		ksft_test_result_fail("%s is %d but child VL is %d\n",
+				      data->default_vl_file,
+				      data->min_vl, child_vl);
+		return;
+	}
+
+	ksft_test_result_pass("%s vector length was inherited\n", data->name);
+
+	file_write_integer(data->default_vl_file, data->default_vl);
+}
+
+/* _ONEXEC takes effect only in the child process */
+void prctl_set_onexec(struct vec_data *data)
+{
+	int ret, child_vl;
+
+	if (data->min_vl == data->max_vl) {
+		ksft_test_result_skip("%s only one VL supported\n",
+				      data->name);
+		return;
+	}
+
+	/* Set a known value for the default and our current VL */
+	ret = file_write_integer(data->default_vl_file, data->max_vl);
+	if (ret != 0)
+		return;
+
+	ret = prctl(data->prctl_set, data->max_vl);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed for %d: %d (%s)\n",
+				      data->name, data->min_vl,
+				      errno, strerror(errno));
+		return;
+	}
+
+	/* Set a different value for the child to have on exec */
+	ret = prctl(data->prctl_set, data->min_vl | PR_SVE_SET_VL_ONEXEC);
+	if (ret < 0) {
+		ksft_test_result_fail("%s prctl set failed for %d: %d (%s)\n",
+				      data->name, data->min_vl,
+				      errno, strerror(errno));
+		return;
+	}
+
+	/* Our current VL should stay the same */
+	if (data->rdvl() != data->max_vl) {
+		ksft_test_result_fail("%s VL changed by _ONEXEC prctl()\n",
+				      data->name);
+		return;
+	}
+
+	/* Check that the child inherited our VL */
+	child_vl = get_child_rdvl(data);
+	if (child_vl != data->min_vl) {
+		ksft_test_result_fail("%s is %d but child VL is %d\n",
+				      data->default_vl_file,
+				      data->min_vl, child_vl);
+		return;
+	}
+
+	ksft_test_result_pass("%s vector length set on exec\n", data->name);
+
+	file_write_integer(data->default_vl_file, data->default_vl);
+}
+
+typedef void (*test_type)(struct vec_data *);
+
+test_type tests[] = {
+	/*
+	 * The default/min/max tests must be first and in this order
+	 * to provide data for other tests.
+	 */
+	proc_read_default,
+	proc_write_min,
+	proc_write_max,
+
+	prctl_get,
+	prctl_set,
+	prctl_set_no_child,
+	prctl_set_for_child,
+	prctl_set_onexec,
+};
+
+int main(void)
+{
+	int i, j;
+
+	ksft_print_header();
+	ksft_set_plan(ARRAY_SIZE(tests) * ARRAY_SIZE(vec_data));
+
+	for (i = 0; i < ARRAY_SIZE(vec_data); i++) {
+		struct vec_data *data = &vec_data[i];
+		int supported = getauxval(data->hwcap_type) & data->hwcap;
+
+		for (j = 0; j < ARRAY_SIZE(tests); j++) {
+			if (supported)
+				tests[j](data);
+			else
+				ksft_test_result_skip("%s not supported\n",
+						      data->name);
+		}
+	}
+
+	ksft_exit_pass();
+}