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(&wall_clock
);
54 high
= ((u64
)__pa(&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
);
81 * If we don't do that, there is the possibility that the guest
82 * will calibrate under heavy load - thus, getting a lower lpj -
83 * and execute the delays themselves without load. This is wrong,
84 * because no delay loop can finish beforehand.
85 * Any heuristics is subject to fail, because ultimately, a large
86 * poll of guests can be running and trouble each other. So we preset
89 static unsigned long kvm_get_tsc_khz(void)
91 struct pvclock_vcpu_time_info
*src
;
92 src
= &per_cpu(hv_clock
, 0);
93 return pvclock_tsc_khz(src
);
96 static void kvm_get_preset_lpj(void)
101 khz
= kvm_get_tsc_khz();
103 lpj
= ((u64
)khz
* 1000);
108 static struct clocksource kvm_clock
= {
110 .read
= kvm_clock_read
,
112 .mask
= CLOCKSOURCE_MASK(64),
113 .mult
= 1 << KVM_SCALE
,
115 .flags
= CLOCK_SOURCE_IS_CONTINUOUS
,
118 static int kvm_register_clock(char *txt
)
120 int cpu
= smp_processor_id();
122 low
= (int)__pa(&per_cpu(hv_clock
, cpu
)) | 1;
123 high
= ((u64
)__pa(&per_cpu(hv_clock
, cpu
)) >> 32);
124 printk(KERN_INFO
"kvm-clock: cpu %d, msr %x:%x, %s\n",
125 cpu
, high
, low
, txt
);
126 return native_write_msr_safe(MSR_KVM_SYSTEM_TIME
, low
, high
);
129 #ifdef CONFIG_X86_LOCAL_APIC
130 static void __cpuinit
kvm_setup_secondary_clock(void)
133 * Now that the first cpu already had this clocksource initialized,
136 WARN_ON(kvm_register_clock("secondary cpu clock"));
137 /* ok, done with our trickery, call native */
138 setup_secondary_APIC_clock();
143 static void __init
kvm_smp_prepare_boot_cpu(void)
145 WARN_ON(kvm_register_clock("primary cpu clock"));
146 native_smp_prepare_boot_cpu();
151 * After the clock is registered, the host will keep writing to the
152 * registered memory location. If the guest happens to shutdown, this memory
153 * won't be valid. In cases like kexec, in which you install a new kernel, this
154 * means a random memory location will be kept being written. So before any
155 * kind of shutdown from our side, we unregister the clock by writting anything
156 * that does not have the 'enable' bit set in the msr
159 static void kvm_crash_shutdown(struct pt_regs
*regs
)
161 native_write_msr_safe(MSR_KVM_SYSTEM_TIME
, 0, 0);
162 native_machine_crash_shutdown(regs
);
166 static void kvm_shutdown(void)
168 native_write_msr_safe(MSR_KVM_SYSTEM_TIME
, 0, 0);
169 native_machine_shutdown();
172 void __init
kvmclock_init(void)
174 if (!kvm_para_available())
177 if (kvmclock
&& kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE
)) {
178 if (kvm_register_clock("boot clock"))
180 pv_time_ops
.get_wallclock
= kvm_get_wallclock
;
181 pv_time_ops
.set_wallclock
= kvm_set_wallclock
;
182 pv_time_ops
.sched_clock
= kvm_clock_read
;
183 pv_time_ops
.get_tsc_khz
= kvm_get_tsc_khz
;
184 #ifdef CONFIG_X86_LOCAL_APIC
185 pv_apic_ops
.setup_secondary_clock
= kvm_setup_secondary_clock
;
188 smp_ops
.smp_prepare_boot_cpu
= kvm_smp_prepare_boot_cpu
;
190 machine_ops
.shutdown
= kvm_shutdown
;
192 machine_ops
.crash_shutdown
= kvm_crash_shutdown
;
194 kvm_get_preset_lpj();
195 clocksource_register(&kvm_clock
);
196 pv_info
.paravirt_enabled
= 1;
197 pv_info
.name
= "KVM";