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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | STANDARDS | HISTORY | CAVEATS | SEE ALSO | COLOPHON |
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PR_SVE_SET_VL(2const) PR_SVE_SET_VL(2const)
PR_SVE_SET_VL - set the thread's SVE vector length
Standard C library (libc, -lc)
#include <linux/prctl.h> /* Definition of PR_* constants */
#include <sys/prctl.h>
int prctl(PR_SVE_SET_VL, unsigned long val);
Configure the thread's SVE vector length, as specified by val.
The bits of val corresponding to PR_SVE_VL_LEN_MASK must be set to
the desired vector length in bytes. This is interpreted as an
upper bound: the kernel will select the greatest available vector
length that does not exceed the value specified. In particular,
specifying SVE_VL_MAX (defined in <asm/sigcontext.h>) for the
PR_SVE_VL_LEN_MASK bits requests the maximum supported vector
length.
In addition, the other bits of val must be set to one of the
following combinations of flags:
0L Perform the change immediately. At the next execve(2) in
the thread, the vector length will be reset to the value
configured in /proc/sys/abi/sve_default_vector_length.
PR_SVE_VL_INHERIT
Perform the change immediately. Subsequent execve(2) calls
will preserve the new vector length.
PR_SVE_SET_VL_ONEXEC
Defer the change, so that it is performed at the next
execve(2) in the thread. Further execve(2) calls will
reset the vector length to the value configured in /proc/
sys/abi/sve_default_vector_length.
PR_SVE_SET_VL_ONEXEC | PR_SVE_VL_INHERIT
Defer the change, so that it is performed at the next
execve(2) in the thread. Further execve(2) calls will
preserve the new vector length.
In all cases, any previously pending deferred change is canceled.
On success, a nonnegative value is returned that describes the
selected configuration. If PR_SVE_SET_VL_ONEXEC was included in
val, then the configuration described by the return value will
take effect at the next execve(2). Otherwise, the configuration
is already in effect when the PR_SVE_SET_VL call returns. In
either case, the value is encoded in the same way as the return
value of PR_SVE_GET_VL. Note that there is no explicit flag in
the return value corresponding to PR_SVE_SET_VL_ONEXEC.
The configuration (including any pending deferred change) is
inherited across fork(2) and clone(2).
On success, PR_SVE_SET_VL returns the nonnegative value described
above. On error, -1 is returned, and errno is set to indicate the
error.
EINVAL SVE is not available on this platform.
EINVAL The value in the bits of val corresponding to
PR_SVE_VL_LEN_MASK is outside the range [SVE_VL_MIN,
SVE_VL_MAX] or is not a multiple of 16.
EINVAL The other bits of val are invalid or unsupported.
/proc/sys/abi/sve_default_vector_length
Linux. arm64 only.
Linux 4.15 (arm64).
Because the compiler or run-time environment may be using SVE,
using this call without the PR_SVE_SET_VL_ONEXEC flag may crash
the calling process. The conditions for using it safely are
complex and system-dependent. Don't use it unless you really know
what you are doing.
prctl(2), PR_SVE_GET_VL(2const)
For more information, see the kernel source file
Documentation/arm64/sve.rst (or Documentation/arm64/sve.txt before
Linux 5.3).
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 PR_SVE_SET_VL(2const)
Pages that refer to this page: prctl(2), PR_SVE_GET_VL(2const)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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