1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #include <sys/types.h>
28 #include <sys/clock.h>
29 #include <sys/panic.h>
30 #include <sys/atomic.h>
31 #include <sys/hypervisor.h>
32
33 #include <sys/archsystm.h>
34
35 /*
36 * On the hypervisor, we have a virtualized system time based upon the
37 * information provided for each VCPU, which is updated every time it is
38 * scheduled onto a real CPU. Thus, none of the traditional code in
39 * i86pc/os/timestamp.c applies, our gethrtime() implementation is run through
40 * the PSM, and there is no scaling step to apply.
41 *
42 * However, the platform does not guarantee monotonicity; thus we have to fake
43 * this up, which is a deeply unpleasant thing to have to do.
44 *
45 * Note that the virtualized interface still relies on the current TSC to
46 * calculate the time in nanoseconds since the VCPU was scheduled, and is thus
47 * subject to all the problems with that. For the most part, the hypervisor is
48 * supposed to deal with them.
49 *
50 * Another wrinkle involves suspend/resume/migration. If we come back and time
51 * is apparently less, we may have resumed on a different machine or on the
52 * same machine after a reboot. In this case we need to maintain an addend to
53 * ensure time continues reasonably. Otherwise we could end up taking a very
54 * long time to expire cyclics in the heap. Thus we have two functions:
55 *
56 * xpv_getsystime()
57 *
58 * The unadulterated system time from the hypervisor. This is only to be
59 * used when programming the hypervisor (setting a timer or calculating
60 * the TOD).
61 *
62 * xpv_gethrtime()
63 *
64 * This is the monotonic hrtime counter to be used by everything else such
65 * as the cyclic subsystem. We should never pass an hrtime directly into
66 * a hypervisor interface, as hrtime_addend may well be non-zero.
67 */
68
69 int hrtime_fake_mt = 1;
70 static volatile hrtime_t hrtime_last;
71 static hrtime_t hrtime_suspend_time;
72 static hrtime_t hrtime_addend;
73
74 /*
75 * These functions are used in DTrace probe context, and must be removed from
76 * fbt consideration. Currently fbt ignores all weak symbols, so this will
77 * achieve that.
78 */
79 #pragma weak xpv_gethrtime = dtrace_xpv_gethrtime
80 #pragma weak xpv_getsystime = dtrace_xpv_getsystime
81 #pragma weak dtrace_gethrtime = dtrace_xpv_gethrtime
82 #pragma weak tsc_read = dtrace_xpv_gethrtime
83
84 hrtime_t
85 dtrace_xpv_getsystime(void)
86 {
87 vcpu_time_info_t *src;
88 vcpu_time_info_t __vti, *dst = &__vti;
89 uint64_t tsc_delta;
90 uint64_t tsc;
91 hrtime_t result;
92 uint32_t stamp;
93
94 src = &CPU->cpu_m.mcpu_vcpu_info->time;
95
96 /*
97 * Loop until version has not been changed during our update, and a Xen
98 * update is not under way (lowest bit is set).
99 */
100 do {
101 dst->version = src->version;
102 stamp = CPU->cpu_m.mcpu_istamp;
103
104 membar_consumer();
105
106 dst->tsc_timestamp = src->tsc_timestamp;
107 dst->system_time = src->system_time;
108 dst->tsc_to_system_mul = src->tsc_to_system_mul;
109 dst->tsc_shift = src->tsc_shift;
110
111 /*
112 * Note that this use of the -actual- TSC register
113 * should probably be the SOLE one in the system on this
114 * paravirtualized platform.
115 */
116 tsc = __rdtsc_insn();
117 tsc_delta = tsc - dst->tsc_timestamp;
118
119 membar_consumer();
120
121 } while (((src->version & 1) | (dst->version ^ src->version)) ||
122 CPU->cpu_m.mcpu_istamp != stamp);
123
124 if (dst->tsc_shift >= 0)
125 tsc_delta <<= dst->tsc_shift;
126 else if (dst->tsc_shift < 0)
127 tsc_delta >>= -dst->tsc_shift;
128
129 result = dst->system_time +
130 ((uint64_t)(tsc_delta * (uint64_t)dst->tsc_to_system_mul) >> 32);
131
132 return (result);
133 }
134
135 hrtime_t
136 dtrace_xpv_gethrtime(void)
137 {
138 hrtime_t result = xpv_getsystime() + hrtime_addend;
139
140 if (hrtime_fake_mt) {
141 hrtime_t last;
142 do {
143 last = hrtime_last;
144 if (result < last)
145 result = last + 1;
146 } while (atomic_cas_64((volatile uint64_t *)&hrtime_last,
147 last, result) != last);
148 }
149
150 return (result);
151 }
152
153 void
154 xpv_time_suspend(void)
155 {
156 hrtime_suspend_time = xpv_getsystime();
157 }
158
159 void
160 xpv_time_resume(void)
161 {
162 hrtime_t delta = xpv_getsystime() - hrtime_suspend_time;
163
164 if (delta < 0)
165 hrtime_addend += -delta;
166 }