135a55149a
Reviewed by: bcr (manpages) Approved by: jtl (co-mentor) MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D25357
79 lines
3.2 KiB
Groff
79 lines
3.2 KiB
Groff
.\" Copyright (c) 2011 Alexander Motin <mav@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 19, 2020
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.Dt APIC 4
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.Os
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.Sh NAME
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.Nm apic
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.Nd Advanced Programmable Interrupt Controller (APIC) driver
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.Sh SYNOPSIS
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This driver is a mandatory part of amd64 kernel.
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To compile this driver into i386 kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device apic"
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.Ed
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.Pp
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The following tunable is settable from the
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.Xr loader 8 :
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.Bl -ohang
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.It Va hint.apic. Ns Ar X Ns Va .clock
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controls event timers functionality support.
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Setting to 0, disables it.
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Default value is 1.
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.It Va hint.apic. Ns Ar X Ns Va .disabled
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Set this to 1 to disable APIC support, falling back to the legacy PIC.
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.El
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.Sh DESCRIPTION
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There are two components in the Intel APIC system, the local APIC (LAPIC)
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and the I/O APIC.
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There is one local APIC in each CPU in the system.
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There is typically one I/O APIC for each peripheral bus in the system.
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.Pp
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Local APICs manage all external interrupts for a specific processor.
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In addition, they are able to accept and generate inter-processor interrupts
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(IPIs).
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.Pp
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I/O APICs contain a redirection table, which is used to route the interrupts
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they receive from peripheral buses to one or more local APICs.
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.Pp
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Each local APIC includes one 32-bit programmable timer.
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This driver uses them to supply kernel with one event timer named "LAPIC".
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Event timer provided by the driver supports both one-shot and periodic modes.
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Because of local APIC nature it is per-CPU.
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The timer frequency is not reported by the platform and so automatically
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measured by the driver on the first use.
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Depending on CPU model this timer may stop in C3 and deeper CPU sleep states.
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Driver automatically adjusts event timer priority and reports it to prevent
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entering dangerous sleep states when it is used.
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.Sh SEE ALSO
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.Xr atrtc 4 ,
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.Xr attimer 4 ,
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.Xr eventtimers 4 ,
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.Xr hpet 4
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