1 /* KVM paravirtual clock driver. A clocksource implementation
2 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
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.
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.
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
19 #include <linux/clocksource.h>
20 #include <linux/kvm_para.h>
21 #include <asm/pvclock.h>
24 #include <linux/percpu.h>
25 #include <linux/hardirq.h>
27 #include <asm/x86_init.h>
28 #include <asm/reboot.h>
30 static int kvmclock = 1;
31 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
32 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
34 static int parse_no_kvmclock(char *arg)
39 early_param("no-kvmclock", parse_no_kvmclock);
41 /* The hypervisor will put information about time periodically here */
42 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
43 static struct pvclock_wall_clock wall_clock;
46 * The wallclock is the time of day when we booted. Since then, some time may
47 * have elapsed since the hypervisor wrote the data. So we try to account for
48 * that with system time
50 static unsigned long kvm_get_wallclock(void)
52 struct pvclock_vcpu_time_info *vcpu_time;
56 low = (int)__pa_symbol(&wall_clock);
57 high = ((u64)__pa_symbol(&wall_clock) >> 32);
59 native_write_msr(msr_kvm_wall_clock, low, high);
61 vcpu_time = &get_cpu_var(hv_clock);
62 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
63 put_cpu_var(hv_clock);
68 static int kvm_set_wallclock(unsigned long now)
73 static cycle_t kvm_clock_read(void)
75 struct pvclock_vcpu_time_info *src;
78 preempt_disable_notrace();
79 src = &__get_cpu_var(hv_clock);
80 ret = pvclock_clocksource_read(src);
81 preempt_enable_notrace();
85 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
87 return kvm_clock_read();
91 * If we don't do that, there is the possibility that the guest
92 * will calibrate under heavy load - thus, getting a lower lpj -
93 * and execute the delays themselves without load. This is wrong,
94 * because no delay loop can finish beforehand.
95 * Any heuristics is subject to fail, because ultimately, a large
96 * poll of guests can be running and trouble each other. So we preset
99 static unsigned long kvm_get_tsc_khz(void)
101 struct pvclock_vcpu_time_info *src;
102 src = &per_cpu(hv_clock, 0);
103 return pvclock_tsc_khz(src);
106 static void kvm_get_preset_lpj(void)
111 khz = kvm_get_tsc_khz();
113 lpj = ((u64)khz * 1000);
118 bool kvm_check_and_clear_guest_paused(void)
121 struct pvclock_vcpu_time_info *src;
124 * per_cpu() is safe here because this function is only called from
125 * timer functions where preemption is already disabled.
127 WARN_ON(!in_atomic());
128 src = &__get_cpu_var(hv_clock);
129 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
130 __this_cpu_and(hv_clock.flags, ~PVCLOCK_GUEST_STOPPED);
137 static struct clocksource kvm_clock = {
139 .read = kvm_clock_get_cycles,
141 .mask = CLOCKSOURCE_MASK(64),
142 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
145 int kvm_register_clock(char *txt)
147 int cpu = smp_processor_id();
150 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
151 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
152 ret = native_write_msr_safe(msr_kvm_system_time, low, high);
153 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
154 cpu, high, low, txt);
159 static void kvm_save_sched_clock_state(void)
163 static void kvm_restore_sched_clock_state(void)
165 kvm_register_clock("primary cpu clock, resume");
168 #ifdef CONFIG_X86_LOCAL_APIC
169 static void __cpuinit kvm_setup_secondary_clock(void)
172 * Now that the first cpu already had this clocksource initialized,
175 WARN_ON(kvm_register_clock("secondary cpu clock"));
180 * After the clock is registered, the host will keep writing to the
181 * registered memory location. If the guest happens to shutdown, this memory
182 * won't be valid. In cases like kexec, in which you install a new kernel, this
183 * means a random memory location will be kept being written. So before any
184 * kind of shutdown from our side, we unregister the clock by writting anything
185 * that does not have the 'enable' bit set in the msr
188 static void kvm_crash_shutdown(struct pt_regs *regs)
190 native_write_msr(msr_kvm_system_time, 0, 0);
191 kvm_disable_steal_time();
192 native_machine_crash_shutdown(regs);
196 static void kvm_shutdown(void)
198 native_write_msr(msr_kvm_system_time, 0, 0);
199 kvm_disable_steal_time();
200 native_machine_shutdown();
203 void __init kvmclock_init(void)
205 if (!kvm_para_available())
208 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
209 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
210 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
211 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
214 printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
215 msr_kvm_system_time, msr_kvm_wall_clock);
217 if (kvm_register_clock("boot clock"))
219 pv_time_ops.sched_clock = kvm_clock_read;
220 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
221 x86_platform.get_wallclock = kvm_get_wallclock;
222 x86_platform.set_wallclock = kvm_set_wallclock;
223 #ifdef CONFIG_X86_LOCAL_APIC
224 x86_cpuinit.early_percpu_clock_init =
225 kvm_setup_secondary_clock;
227 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
228 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
229 machine_ops.shutdown = kvm_shutdown;
231 machine_ops.crash_shutdown = kvm_crash_shutdown;
233 kvm_get_preset_lpj();
234 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
235 pv_info.paravirt_enabled = 1;
236 pv_info.name = "KVM";
238 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
239 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);