vmm_ipi.c revision 266339 
1/*-
2 * Copyright (c) 2011 NetApp, Inc.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: stable/10/sys/amd64/vmm/vmm_ipi.c 266339 2014-05-17 19:11:08Z jhb $
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD: stable/10/sys/amd64/vmm/vmm_ipi.c 266339 2014-05-17 19:11:08Z jhb $");
31
32#include <sys/param.h>
33#include <sys/systm.h>
34#include <sys/proc.h>
35#include <sys/bus.h>
36
37#include <machine/intr_machdep.h>
38#include <machine/apicvar.h>
39#include <machine/segments.h>
40#include <machine/md_var.h>
41
42#include <machine/vmm.h>
43#include "vmm_ipi.h"
44
45extern inthand_t IDTVEC(rsvd), IDTVEC(justreturn);
46
47CTASSERT(APIC_SPURIOUS_INT == 255);
48
49int
50vmm_ipi_alloc(void)
51{
52	int idx;
53	uintptr_t func;
54	struct gate_descriptor *ip;
55
56	/*
57	 * Search backwards from the highest IDT vector available for use
58	 * as our IPI vector. We install the 'justreturn' handler at that
59	 * vector and use it to interrupt the vcpus.
60	 *
61	 * We do this because the IPI_AST is heavyweight and saves all
62	 * registers in the trapframe. This is overkill for our use case
63	 * which is simply to EOI the interrupt and return.
64	 */
65	idx = APIC_SPURIOUS_INT;
66	while (--idx >= APIC_IPI_INTS) {
67		ip = &idt[idx];
68		func = ((long)ip->gd_hioffset << 16 | ip->gd_looffset);
69		if (func == (uintptr_t)&IDTVEC(rsvd)) {
70			setidt(idx , IDTVEC(justreturn), SDT_SYSIGT,
71			       SEL_KPL, 0);
72			return (idx);
73		}
74	}
75	return (0);
76}
77
78void
79vmm_ipi_free(int ipinum)
80{
81	uintptr_t func;
82	struct gate_descriptor *ip;
83
84	KASSERT(ipinum >= APIC_IPI_INTS && ipinum < APIC_SPURIOUS_INT,
85	    ("invalid ipi %d", ipinum));
86
87	ip = &idt[ipinum];
88	func = ((long)ip->gd_hioffset << 16 | ip->gd_looffset);
89	KASSERT(func == (uintptr_t)&IDTVEC(justreturn),
90	    ("invalid ipi %d", ipinum));
91
92	setidt(ipinum, IDTVEC(rsvd), SDT_SYSIGT, SEL_KPL, 0);
93}
94