s390_sthyi - emulate STHYI instruction
#include <asm/unistd.h>
int s390_sthyi(unsigned long function_code, void *resp_buffer,
uint64_t *return_code, unsigned long flags);
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.
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.
- 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.
This system call is available since Linux 4.15.
This Linux-specific system call is available only on the s390 architecture.
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
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.
syscall(2)