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S390_STHYI(2)                 System Calls Manual                S390_STHYI(2)
NAME
       s390_sthyi - emulate STHYI instruction
SYNOPSIS
       #include <asm/unistd.h>
       int s390_sthyi(unsigned long function_code, void *resp_buffer,
                      uint64_t *return_code, unsigned long flags);
DESCRIPTION
       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.
       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 instruc-
       tion, 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 cur-
       rently must be set to 0.
RETURN VALUE
       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
       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
       This system call is available since Linux 4.15.
CONFORMING TO
       This Linux-specific system call is available only on the s390 architec-
       ture.
NOTES
       Glibc does not provide a wrapper for this system call,  use  syscall(2)
       to call it.
       For  details of the STHYI instruction, see <https://www.ibm.com/support
       /knowledgecenter/SSB27U_6.3.0/com.ibm.zvm.v630.hcpb4/hcpb4sth.htm>.
SEE ALSO
       syscall(2)
COLOPHON
       This page is part of release 4.15 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         2018-02-02                     S390_STHYI(2)