s390_sthyi(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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);

       Note: There is no glibc wrapper for this system call; see NOTES.

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 to indicate the error.

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 failed.

       EOPNOTSUPP
              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
       architecture.

NOTES         top

       Glibc does not provide a wrapper for this system call; call it
       using syscall(2)

       For details of the STHYI instruction, see the documentation page
       
       ⟨https://www.ibm.com/support/knowledgecenter/SSB27U_6.3.0/com.ibm.zvm.v630.hcpb4/hcpb4sth.htm⟩.

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

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

SEE ALSO         top

       syscall(2)

COLOPHON         top

       This page is part of release 5.11 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
       https://www.kernel.org/doc/man-pages/.

Linux Programmer's Manual      2021-03-22                  S390_STHYI(2)

Pages that refer to this page: syscalls(2)