s390_sthyi(2) — Linux manual page


S390_STHYI(2)                System Calls Manual               S390_STHYI(2)

NAME         top

       s390_sthyi - emulate STHYI instruction

SYNOPSIS         top

       #include <asm/unistd.h>

       int s390_sthyi(unsigned long function_code, void *resp_buffer,
                      uint64_t *return_code, unsigned long flags);

DESCRIPTION         top

       The s390_sthyi() system call emulates the STHYI (Store Hypervisor
       Information) instruction.  It provides hardware resource information
       for the machine and its virtualization levels.  This includes CPU
       type and capacity, as well as the machine model and other metrics.

       The function_code argument indicates which function to perform.  The
       following code(s) are supported:

       0      Return CP (Central Processor) and IFL (Integrated Facility for
              Linux) capacity information.

       The resp_buffer argument specifies the address of a response buffer.
       When the function_code is 0, the buffer must be one page (4K) in
       size.  If the system call returns 0, the response buffer will be
       filled with CPU capacity information.  Otherwise, the response
       buffer's content is unchanged.

       The return_code argument stores the return code of the STHYI
       instruction, using one of the following values:

       0      Success.

       4      Unsupported function code.

       For further details about return_code, function_code, and
       resp_buffer, see the reference given in NOTES.

       The flags argument is provided to allow for future extensions and
       currently must be set to 0.

RETURN VALUE         top

       On success (that is: emulation succeeded), the return value of
       s390_sthyi() matches the condition code of the STHYI instructions,
       which is a value in the range [0..3].  A return value of 0 indicates
       that CPU capacity information is stored in *resp_buffer.  A return
       value of 3 indicates "unsupported function code" and the content of
       *resp_buffer is unchanged.  The return values 1 and 2 are reserved.

       On error, -1 is returned, and errno is set appropriately.

ERRORS         top

       EFAULT The value specified in resp_buffer or return_code is not a
              valid address.

       EINVAL The value specified in flags is nonzero.

       ENOMEM Allocating memory for handling the CPU capacity information

              The value specified in function_code is not valid.

VERSIONS         top

       This system call is available since Linux 4.15.

CONFORMING TO         top

       This Linux-specific system call is available only on the s390

NOTES         top

       Glibc does not provide a wrapper for this system call, use syscall(2)
       to call it.

       For details of the STHYI instruction, see the documentation page 

       When the system call interface is used, the response buffer doesn't
       have to fulfill alignment requirements described in the STHYI in‐
       struction definition.

       The kernel caches the response (for up to one second, as of Linux
       4.16).  Subsequent system call invocations may return the cached re‐

SEE ALSO         top


COLOPHON         top

       This page is part of release 5.09 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux Programmer's Manual        2020-04-11                    S390_STHYI(2)

Pages that refer to this page: syscalls(2)