1/*  KVM paravirtual clock driver. A clocksource implementation
2    Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
3
4    This program is free software; you can redistribute it and/or modify
5    it under the terms of the GNU General Public License as published by
6    the Free Software Foundation; either version 2 of the License, or
7    (at your option) any later version.
8
9    This program is distributed in the hope that it will be useful,
10    but WITHOUT ANY WARRANTY; without even the implied warranty of
11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12    GNU General Public License for more details.
13
14    You should have received a copy of the GNU General Public License
15    along with this program; if not, write to the Free Software
16    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
17*/
18
19#include <linux/clocksource.h>
20#include <linux/kvm_para.h>
21#include <asm/pvclock.h>
22#include <asm/msr.h>
23#include <asm/apic.h>
24#include <linux/percpu.h>
25
26#include <asm/x86_init.h>
27#include <asm/reboot.h>
28
29static int kvmclock = 1;
30static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
31static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
32
33static int parse_no_kvmclock(char *arg)
34{
35	kvmclock = 0;
36	return 0;
37}
38early_param("no-kvmclock", parse_no_kvmclock);
39
40/* The hypervisor will put information about time periodically here */
41static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
42static struct pvclock_wall_clock wall_clock;
43
44/*
45 * The wallclock is the time of day when we booted. Since then, some time may
46 * have elapsed since the hypervisor wrote the data. So we try to account for
47 * that with system time
48 */
49static unsigned long kvm_get_wallclock(void)
50{
51	struct pvclock_vcpu_time_info *vcpu_time;
52	struct timespec ts;
53	int low, high;
54
55	low = (int)__pa_symbol(&wall_clock);
56	high = ((u64)__pa_symbol(&wall_clock) >> 32);
57
58	native_write_msr(msr_kvm_wall_clock, low, high);
59
60	vcpu_time = &get_cpu_var(hv_clock);
61	pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
62	put_cpu_var(hv_clock);
63
64	return ts.tv_sec;
65}
66
67static int kvm_set_wallclock(unsigned long now)
68{
69	return -1;
70}
71
72static cycle_t kvm_clock_read(void)
73{
74	struct pvclock_vcpu_time_info *src;
75	cycle_t ret;
76
77	preempt_disable_notrace();
78	src = &__get_cpu_var(hv_clock);
79	ret = pvclock_clocksource_read(src);
80	preempt_enable_notrace();
81	return ret;
82}
83
84static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
85{
86	return kvm_clock_read();
87}
88
89/*
90 * If we don't do that, there is the possibility that the guest
91 * will calibrate under heavy load - thus, getting a lower lpj -
92 * and execute the delays themselves without load. This is wrong,
93 * because no delay loop can finish beforehand.
94 * Any heuristics is subject to fail, because ultimately, a large
95 * poll of guests can be running and trouble each other. So we preset
96 * lpj here
97 */
98static unsigned long kvm_get_tsc_khz(void)
99{
100	struct pvclock_vcpu_time_info *src;
101	src = &per_cpu(hv_clock, 0);
102	return pvclock_tsc_khz(src);
103}
104
105static void kvm_get_preset_lpj(void)
106{
107	unsigned long khz;
108	u64 lpj;
109
110	khz = kvm_get_tsc_khz();
111
112	lpj = ((u64)khz * 1000);
113	do_div(lpj, HZ);
114	preset_lpj = lpj;
115}
116
117static struct clocksource kvm_clock = {
118	.name = "kvm-clock",
119	.read = kvm_clock_get_cycles,
120	.rating = 400,
121	.mask = CLOCKSOURCE_MASK(64),
122	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
123};
124
125int kvm_register_clock(char *txt)
126{
127	int cpu = smp_processor_id();
128	int low, high, ret;
129
130	low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
131	high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
132	ret = native_write_msr_safe(msr_kvm_system_time, low, high);
133	printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
134	       cpu, high, low, txt);
135
136	return ret;
137}
138
139static void kvm_save_sched_clock_state(void)
140{
141}
142
143static void kvm_restore_sched_clock_state(void)
144{
145	kvm_register_clock("primary cpu clock, resume");
146}
147
148#ifdef CONFIG_X86_LOCAL_APIC
149static void __cpuinit kvm_setup_secondary_clock(void)
150{
151	/*
152	 * Now that the first cpu already had this clocksource initialized,
153	 * we shouldn't fail.
154	 */
155	WARN_ON(kvm_register_clock("secondary cpu clock"));
156}
157#endif
158
159/*
160 * After the clock is registered, the host will keep writing to the
161 * registered memory location. If the guest happens to shutdown, this memory
162 * won't be valid. In cases like kexec, in which you install a new kernel, this
163 * means a random memory location will be kept being written. So before any
164 * kind of shutdown from our side, we unregister the clock by writting anything
165 * that does not have the 'enable' bit set in the msr
166 */
167#ifdef CONFIG_KEXEC
168static void kvm_crash_shutdown(struct pt_regs *regs)
169{
170	native_write_msr(msr_kvm_system_time, 0, 0);
171	kvm_disable_steal_time();
172	native_machine_crash_shutdown(regs);
173}
174#endif
175
176static void kvm_shutdown(void)
177{
178	native_write_msr(msr_kvm_system_time, 0, 0);
179	kvm_disable_steal_time();
180	native_machine_shutdown();
181}
182
183void __init kvmclock_init(void)
184{
185	if (!kvm_para_available())
186		return;
187
188	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
189		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
190		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
191	} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
192		return;
193
194	printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
195		msr_kvm_system_time, msr_kvm_wall_clock);
196
197	if (kvm_register_clock("boot clock"))
198		return;
199	pv_time_ops.sched_clock = kvm_clock_read;
200	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
201	x86_platform.get_wallclock = kvm_get_wallclock;
202	x86_platform.set_wallclock = kvm_set_wallclock;
203#ifdef CONFIG_X86_LOCAL_APIC
204	x86_cpuinit.early_percpu_clock_init =
205		kvm_setup_secondary_clock;
206#endif
207	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
208	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
209	machine_ops.shutdown  = kvm_shutdown;
210#ifdef CONFIG_KEXEC
211	machine_ops.crash_shutdown  = kvm_crash_shutdown;
212#endif
213	kvm_get_preset_lpj();
214	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
215	pv_info.paravirt_enabled = 1;
216	pv_info.name = "KVM";
217
218	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
219		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
220}
221