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
29 static int kvmclock = 1;
30 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
31 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
32
parse_no_kvmclock(char * arg)33 static int parse_no_kvmclock(char *arg)
34 {
35 kvmclock = 0;
36 return 0;
37 }
38 early_param("no-kvmclock", parse_no_kvmclock);
39
40 /* The hypervisor will put information about time periodically here */
41 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
42 static 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 */
kvm_get_wallclock(void)49 static 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
kvm_set_wallclock(unsigned long now)67 static int kvm_set_wallclock(unsigned long now)
68 {
69 return -1;
70 }
71
kvm_clock_read(void)72 static 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
kvm_clock_get_cycles(struct clocksource * cs)84 static 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 */
kvm_get_tsc_khz(void)98 static 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
kvm_get_preset_lpj(void)105 static 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
117 static 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
kvm_register_clock(char * txt)125 int 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
kvm_save_sched_clock_state(void)139 static void kvm_save_sched_clock_state(void)
140 {
141 }
142
kvm_restore_sched_clock_state(void)143 static void kvm_restore_sched_clock_state(void)
144 {
145 kvm_register_clock("primary cpu clock, resume");
146 }
147
148 #ifdef CONFIG_X86_LOCAL_APIC
kvm_setup_secondary_clock(void)149 static 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
kvm_crash_shutdown(struct pt_regs * regs)168 static 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
kvm_shutdown(void)176 static 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
kvmclock_init(void)183 void __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