1/*  paravirtual clock -- common code used by kvm/xen
2
3    This program is free software; you can redistribute it and/or modify
4    it under the terms of the GNU General Public License as published by
5    the Free Software Foundation; either version 2 of the License, or
6    (at your option) any later version.
7
8    This program is distributed in the hope that it will be useful,
9    but WITHOUT ANY WARRANTY; without even the implied warranty of
10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11    GNU General Public License for more details.
12
13    You should have received a copy of the GNU General Public License
14    along with this program; if not, write to the Free Software
15    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
16*/
17
18#include <linux/kernel.h>
19#include <linux/percpu.h>
20#include <linux/notifier.h>
21#include <linux/sched.h>
22#include <linux/gfp.h>
23#include <linux/bootmem.h>
24#include <asm/fixmap.h>
25#include <asm/pvclock.h>
26
27static u8 valid_flags __read_mostly = 0;
28
29void pvclock_set_flags(u8 flags)
30{
31	valid_flags = flags;
32}
33
34unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
35{
36	u64 pv_tsc_khz = 1000000ULL << 32;
37
38	do_div(pv_tsc_khz, src->tsc_to_system_mul);
39	if (src->tsc_shift < 0)
40		pv_tsc_khz <<= -src->tsc_shift;
41	else
42		pv_tsc_khz >>= src->tsc_shift;
43	return pv_tsc_khz;
44}
45
46void pvclock_touch_watchdogs(void)
47{
48	touch_softlockup_watchdog_sync();
49	clocksource_touch_watchdog();
50	rcu_cpu_stall_reset();
51	reset_hung_task_detector();
52}
53
54static atomic64_t last_value = ATOMIC64_INIT(0);
55
56void pvclock_resume(void)
57{
58	atomic64_set(&last_value, 0);
59}
60
61u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
62{
63	unsigned version;
64	cycle_t ret;
65	u8 flags;
66
67	do {
68		version = __pvclock_read_cycles(src, &ret, &flags);
69	} while ((src->version & 1) || version != src->version);
70
71	return flags & valid_flags;
72}
73
74cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
75{
76	unsigned version;
77	cycle_t ret;
78	u64 last;
79	u8 flags;
80
81	do {
82		version = __pvclock_read_cycles(src, &ret, &flags);
83	} while ((src->version & 1) || version != src->version);
84
85	if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
86		src->flags &= ~PVCLOCK_GUEST_STOPPED;
87		pvclock_touch_watchdogs();
88	}
89
90	if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
91		(flags & PVCLOCK_TSC_STABLE_BIT))
92		return ret;
93
94	/*
95	 * Assumption here is that last_value, a global accumulator, always goes
96	 * forward. If we are less than that, we should not be much smaller.
97	 * We assume there is an error marging we're inside, and then the correction
98	 * does not sacrifice accuracy.
99	 *
100	 * For reads: global may have changed between test and return,
101	 * but this means someone else updated poked the clock at a later time.
102	 * We just need to make sure we are not seeing a backwards event.
103	 *
104	 * For updates: last_value = ret is not enough, since two vcpus could be
105	 * updating at the same time, and one of them could be slightly behind,
106	 * making the assumption that last_value always go forward fail to hold.
107	 */
108	last = atomic64_read(&last_value);
109	do {
110		if (ret < last)
111			return last;
112		last = atomic64_cmpxchg(&last_value, last, ret);
113	} while (unlikely(last != ret));
114
115	return ret;
116}
117
118void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
119			    struct pvclock_vcpu_time_info *vcpu_time,
120			    struct timespec *ts)
121{
122	u32 version;
123	u64 delta;
124	struct timespec now;
125
126	/* get wallclock at system boot */
127	do {
128		version = wall_clock->version;
129		rmb();		/* fetch version before time */
130		now.tv_sec  = wall_clock->sec;
131		now.tv_nsec = wall_clock->nsec;
132		rmb();		/* fetch time before checking version */
133	} while ((wall_clock->version & 1) || (version != wall_clock->version));
134
135	delta = pvclock_clocksource_read(vcpu_time);	/* time since system boot */
136	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
137
138	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
139	now.tv_sec = delta;
140
141	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
142}
143
144#ifdef CONFIG_X86_64
145/*
146 * Initialize the generic pvclock vsyscall state.  This will allocate
147 * a/some page(s) for the per-vcpu pvclock information, set up a
148 * fixmap mapping for the page(s)
149 */
150
151int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
152				 int size)
153{
154	int idx;
155
156	WARN_ON (size != PVCLOCK_VSYSCALL_NR_PAGES*PAGE_SIZE);
157
158	for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
159		__set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
160			     __pa(i) + (idx*PAGE_SIZE),
161			     PAGE_KERNEL_VVAR);
162	}
163
164	return 0;
165}
166#endif
167