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 <asm/reboot.h>
29 static int kvmclock = 1;
31 static int parse_no_kvmclock(char *arg)
36 early_param("no-kvmclock", parse_no_kvmclock);
38 /* The hypervisor will put information about time periodically here */
39 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
40 static struct pvclock_wall_clock wall_clock;
43 * The wallclock is the time of day when we booted. Since then, some time may
44 * have elapsed since the hypervisor wrote the data. So we try to account for
45 * that with system time
47 static unsigned long kvm_get_wallclock(void)
49 struct pvclock_vcpu_time_info *vcpu_time;
53 low = (int)__pa_symbol(&wall_clock);
54 high = ((u64)__pa_symbol(&wall_clock) >> 32);
55 native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
57 vcpu_time = &get_cpu_var(hv_clock);
58 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
59 put_cpu_var(hv_clock);
64 static int kvm_set_wallclock(unsigned long now)
69 static cycle_t kvm_clock_read(void)
71 struct pvclock_vcpu_time_info *src;
74 src = &get_cpu_var(hv_clock);
75 ret = pvclock_clocksource_read(src);
76 put_cpu_var(hv_clock);
80 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
82 return kvm_clock_read();
86 * If we don't do that, there is the possibility that the guest
87 * will calibrate under heavy load - thus, getting a lower lpj -
88 * and execute the delays themselves without load. This is wrong,
89 * because no delay loop can finish beforehand.
90 * Any heuristics is subject to fail, because ultimately, a large
91 * poll of guests can be running and trouble each other. So we preset
94 static unsigned long kvm_get_tsc_khz(void)
96 struct pvclock_vcpu_time_info *src;
97 src = &per_cpu(hv_clock, 0);
98 return pvclock_tsc_khz(src);
101 static void kvm_get_preset_lpj(void)
106 khz = kvm_get_tsc_khz();
108 lpj = ((u64)khz * 1000);
113 static struct clocksource kvm_clock = {
115 .read = kvm_clock_get_cycles,
117 .mask = CLOCKSOURCE_MASK(64),
118 .mult = 1 << KVM_SCALE,
120 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
123 static int kvm_register_clock(char *txt)
125 int cpu = smp_processor_id();
127 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
128 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
129 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
130 cpu, high, low, txt);
131 return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
134 #ifdef CONFIG_X86_LOCAL_APIC
135 static void __cpuinit kvm_setup_secondary_clock(void)
138 * Now that the first cpu already had this clocksource initialized,
141 WARN_ON(kvm_register_clock("secondary cpu clock"));
142 /* ok, done with our trickery, call native */
143 setup_secondary_APIC_clock();
148 static void __init kvm_smp_prepare_boot_cpu(void)
150 WARN_ON(kvm_register_clock("primary cpu clock"));
151 native_smp_prepare_boot_cpu();
156 * After the clock is registered, the host will keep writing to the
157 * registered memory location. If the guest happens to shutdown, this memory
158 * won't be valid. In cases like kexec, in which you install a new kernel, this
159 * means a random memory location will be kept being written. So before any
160 * kind of shutdown from our side, we unregister the clock by writting anything
161 * that does not have the 'enable' bit set in the msr
164 static void kvm_crash_shutdown(struct pt_regs *regs)
166 native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
167 native_machine_crash_shutdown(regs);
171 static void kvm_shutdown(void)
173 native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
174 native_machine_shutdown();
177 void __init kvmclock_init(void)
179 if (!kvm_para_available())
182 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
183 if (kvm_register_clock("boot clock"))
185 pv_time_ops.get_wallclock = kvm_get_wallclock;
186 pv_time_ops.set_wallclock = kvm_set_wallclock;
187 pv_time_ops.sched_clock = kvm_clock_read;
188 pv_time_ops.get_tsc_khz = kvm_get_tsc_khz;
189 #ifdef CONFIG_X86_LOCAL_APIC
190 pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
193 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
195 machine_ops.shutdown = kvm_shutdown;
197 machine_ops.crash_shutdown = kvm_crash_shutdown;
199 kvm_get_preset_lpj();
200 clocksource_register(&kvm_clock);
201 pv_info.paravirt_enabled = 1;
202 pv_info.name = "KVM";