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 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

       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 architecture.

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/.