man2/s390_sthyi.2

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   2 .\" Author: QingFeng Hao <haoqf@linux.vnet.ibm.com>
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  25 .TH S390_STHYI 2 2017-09-21 "Linux Programmer's Manual"
  26 .SH NAME
  27 s390_sthyi \- emulate STHYI instruction
  28 .SH SYNOPSIS
  29 .nf
  30 .B #include <asm/unistd.h>
  31 .PP
  32 .BI "int s390_sthyi(unsigned long " function_code ", void *" buffer ",
  33 .BI "               uint64_t *" return_code ", unsigned long " flags ");
  34 .fi
  35 .SH DESCRIPTION
  36 The
  37 .BR s390_sthyi ()
  38 system call emulates the STHYI (Store Hypervisor Information) instruction.
  39 It provides hardware resource information for the machine and its
  40 virtualization levels.
  41 This includes CPU type and capacity, as well as the machine model and
  42 other metrics.
  43 .PP
  44 The
  45 .I function_code
  46 argument indicates which function to perform.
  47 The following code(s) are supported:
  48 .TP
  49 0
  50 Return CP (Central Processor) and IFL (Integrated Facility for Linux)
  51 capacity information.
  52 .PP
  53 The
  54 .I buffer
  55 argument specifies the address of a response buffer.
  56 If the system call returns 0,
  57 the response buffer will be filled with CPU capacity information.
  58 Otherwise, the response buffer's content is unchanged.
  59 .PP
  60 The
  61 .I return_code
  62 argument stores the return code of the STHYI instruction,
  63 using one of the following values:
  64 .TP 8
  65 0
  66 Success.
  67 .TP
  68 4
  69 Unsupported function code.
  70 .PP
  71 For further details about
  72 .IR return_code ,
  73 .IR function_code ,
  74 and
  75 .IR buffer ,
  76 please see section
  77 CONFORMING TO
  78 below.
  79 .PP
  80 The
  81 .I flags
  82 argument is provided to allow for future extensions and currently
  83 must be set to 0.
  84 .SH RETURN VALUE
  85 On success (that is: emulation succeeded), the return value of
  86 .BR s390_sthyi ()
  87 matches the condition code of the STHYI instructions, which is a value
  88 in the range [0..3].
  89 A return value of 0 indicates that CPU capacity information is stored in
  90 .IR *buffer .
  91 A return value of 3 indicates "unsupported function code" and the content of
  92 .IR *buffer
  93 is unchanged.
  94 The return values 1 and 2 are reserved.
  95 .PP
  96 On error, \-1 is returned, and
  97 .IR errno
  98 is set appropriately.
  99 .SH ERRORS
 100 .TP
 101 .B EFAULT
 102 The value specified in
 103 .I buffer
 104 or
 105 .I return_code
 106 is not a valid address.
 107 .TP
 108 .B EINVAL
 109 The value specified in
 110 .I flags
 111 is nonzero.
 112 .TP
 113 .B ENOMEM
 114 Allocating memory for handling the CPU capacity information failed.
 115 .TP
 116 .B EOPNOTSUPP
 117 The value specified in
 118 .I function_code
 119 is not valid.
 120 .SH VERSIONS
 121 This system call is available since Linux 4.15.
 122 .SH CONFORMING TO
 123 This Linux-specific system call is available only on the s390 architecture.
 124 For details of the STHYI instruction, see
 125 .UR https://www.ibm.com\:/support\:/knowledgecenter\:/SSB27U_6.3.0\:/com.ibm.zvm.v630.hcpb4\:/hcpb4sth.htm
 126 .UE .
 127 .SH NOTES
 128 Glibc does not provide a wrapper for this system call, use
 129 .BR syscall (2)
 130 to call it.
 131 .SH SEE ALSO
 132 .BR syscall (2)