Provided by: manpages-dev_6.8-2_all bug

NAME

       s390_sthyi - emulate STHYI instruction

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <asm/sthyi.h>        /* Definition of STHYI_* constants */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_s390_sthyi, unsigned long function_code,
                   void *resp_buffer, uint64_t *return_code,
                   unsigned long flags);

       Note: glibc provides no wrapper for s390_sthyi(), necessitating the use of syscall(2).

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:

       STHYI_FC_CP_IFL_CAP
              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
       STHYI_FC_CP_IFL_CAP, 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

       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

       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.

STANDARDS

       Linux on s390.

HISTORY

       Linux 4.15.

NOTES

       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

       syscall(2)