s390_sthyi

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.
       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
       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 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)

COLOPHON
       This page is part of release 5.10 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          2020-04-11                      S390_STHYI(2)