169 lines
4.7 KiB
Groff
169 lines
4.7 KiB
Groff
.\" $NetBSD: x86_64_get_mtrr.2,v 1.8 2008/04/30 13:10:50 martin Exp $
|
|
.\"
|
|
.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Gregory McGarry.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd November 10, 2001
|
|
.Dt X86_64_GET_MTRR 2 x86_64
|
|
.Os
|
|
.Sh NAME
|
|
.Nm x86_64_get_mtrr ,
|
|
.Nm x86_64_set_mtrr
|
|
.Nd access Memory Type Range Registers
|
|
.Sh LIBRARY
|
|
.Lb libx86_64
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In machine/sysarch.h
|
|
.In machine/mtrr.h
|
|
.Ft int
|
|
.Fn x86_64_get_mtrr "struct mtrr *mtrrp" "int *n"
|
|
.Ft int
|
|
.Fn x86_64_set_mtrr "struct mtrr *mtrrp" "int *n"
|
|
.Sh DESCRIPTION
|
|
These functions provide an interface to the MTRR registers found on
|
|
686-class processors for controlling processor access to memory ranges.
|
|
This is most useful for accessing devices such as video accelerators on
|
|
.Xr pci 4
|
|
and
|
|
.Xr agp 4
|
|
buses.
|
|
For example, enabling write-combining allows bus-write transfers
|
|
to be combined into a larger transfer before bursting over the bus.
|
|
This can increase performance of write operations 2.5 times or more.
|
|
.Pp
|
|
.Fa mtrrp
|
|
is a pointer to one or more mtrr structures, as described below.
|
|
The
|
|
.Fa n
|
|
argument is a pointer to an integer containing the number of structures
|
|
pointed to by
|
|
.Fa mtrrp .
|
|
For
|
|
.Fn x86_64_set_mtrr
|
|
the integer pointed to by
|
|
.Fa n
|
|
will be updated to reflect the actual number of MTRRs successfully set.
|
|
For
|
|
.Fn x86_64_get_mtrr
|
|
no more than
|
|
.Fa n
|
|
structures will be copied out, and the integer value pointed to by
|
|
.Fa n
|
|
will be updated to reflect the actual number of valid structures retrieved.
|
|
A
|
|
.Dv NULL
|
|
argument to
|
|
.Fa mtrrp
|
|
will result in just the number of MTRRs available being returned
|
|
in the integer pointed to by
|
|
.Fa n .
|
|
.Pp
|
|
The argument
|
|
.Fa mtrrp
|
|
has the following structure:
|
|
.Bd -literal
|
|
struct mtrr {
|
|
uint64_t base;
|
|
uint64_t len;
|
|
uint8_t type;
|
|
int flags;
|
|
pid_t owner;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The location of the mapping is described by its physical base address
|
|
.Em base
|
|
and length
|
|
.Em len .
|
|
Valid values for
|
|
.Em type
|
|
are:
|
|
.Pp
|
|
.Bl -tag -offset indent -width MTRR_TYPE_UNDEF1 -compact
|
|
.It MTRR_TYPE_UC
|
|
uncached memory
|
|
.It MTRR_TYPE_WC
|
|
use write-combining
|
|
.It MTRR_TYPE_WT
|
|
use write-through caching
|
|
.It MTRR_TYPE_WP
|
|
write-protected memory
|
|
.It MTRR_TYPE_WB
|
|
use write-back caching
|
|
.El
|
|
.Pp
|
|
Valid values for
|
|
.Em flags
|
|
are:
|
|
.Pp
|
|
.Bl -tag -offset indent -width MTRR_PRIVATE -compact
|
|
.It MTRR_PRIVATE
|
|
own range, reset the MTRR when the current process exits
|
|
.It MTRR_FIXED
|
|
use fixed range MTRR
|
|
.It MTRR_VALID
|
|
entry is valid
|
|
.El
|
|
.Pp
|
|
The
|
|
.Em owner
|
|
member is the PID of the user process which claims the mapping.
|
|
It is only valid if MTRR_PRIVATE is set in
|
|
.Em flags .
|
|
To clear/reset MTRRs, use a
|
|
.Em flags
|
|
field without MTRR_VALID set.
|
|
.Sh RETURN VALUES
|
|
Upon successful completion zero is returned, otherwise \-1 is returned
|
|
on failure, and the global variable
|
|
.Va errno
|
|
is set to indicate the error.
|
|
The integer value pointed to by
|
|
.Fa n
|
|
will contain the number of successfully processed mtrr structures
|
|
in both cases.
|
|
.Sh ERRORS
|
|
.Bl -tag -width [EINVAL]
|
|
.It Bq Er ENOSYS
|
|
The currently running kernel or CPU has no MTRR support.
|
|
.It Bq Er EINVAL
|
|
The currently running kernel has no MTRR support, or one of the mtrr
|
|
structures pointed to by
|
|
.Fa mtrrp
|
|
is invalid.
|
|
.It Bq Er EBUSY
|
|
No unused MTRRs are available.
|
|
.El
|
|
.Sh HISTORY
|
|
The
|
|
.Fn x86_64_get_mtrr
|
|
and
|
|
.Fn x86_64_set_mtrr
|
|
were derived from their i386 counterparts, which appeared in
|
|
.Nx 1.6 .
|