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Test Your Knowledge in Computers #281
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A hypervisor or virtual machine monitor (VMM) is a computer software, firmware or hardware that creates and runs virtual private networks.
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IOPL(2) 						     Linux Programmer's Manual							   IOPL(2)

NAME
iopl - change I/O privilege level SYNOPSIS
#include <sys/io.h> int iopl(int level); DESCRIPTION
iopl changes the I/O privilege level of the current process, as specified in level. This call is necessary to allow 8514-compatible X servers to run under Linux. Since these X servers require access to all 65536 I/O ports, the ioperm call is not sufficient. In addition to granting unrestricted I/O port access, running at a higher I/O privilege level also allows the process to disable inter- rupts. This will probably crash the system, and is not recommended. Permissions are inherited by fork and exec. The I/O privilege level for a normal process is 0. RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately. ERRORS
EINVAL level is greater than 3. EPERM The current user is not the super-user. CONFORMING TO
iopl is Linux specific and should not be used in processes intended to be portable. NOTES
Libc5 treats it as a system call and has a prototype in <unistd.h>. Glibc1 does not have a prototype. Glibc2 has a prototype both in <sys/io.h> and in <sys/perm.h>. Avoid the latter, it is available on i386 only. SEE ALSO
ioperm(2) Linux 0.99.11 1993-07-24 IOPL(2)

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