blob: 6389a6bca11b8159e47eab9feff42b828f666fc2 [file] [log] [blame]
/* KVM paravirtual clock driver. A clocksource implementation
Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#include <linux/clocksource.h>
#include <linux/kvm_para.h>
#include <asm/pvclock.h>
#include <asm/msr.h>
#include <asm/apic.h>
#include <linux/percpu.h>
#include <asm/x86_init.h>
#include <asm/reboot.h>
static int kvmclock = 1;
static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
static int parse_no_kvmclock(char *arg)
kvmclock = 0;
return 0;
early_param("no-kvmclock", parse_no_kvmclock);
/* The hypervisor will put information about time periodically here */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
static struct pvclock_wall_clock wall_clock;
* The wallclock is the time of day when we booted. Since then, some time may
* have elapsed since the hypervisor wrote the data. So we try to account for
* that with system time
static unsigned long kvm_get_wallclock(void)
struct pvclock_vcpu_time_info *vcpu_time;
struct timespec ts;
int low, high;
low = (int)__pa_symbol(&wall_clock);
high = ((u64)__pa_symbol(&wall_clock) >> 32);
native_write_msr(msr_kvm_wall_clock, low, high);
vcpu_time = &get_cpu_var(hv_clock);
pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
return ts.tv_sec;
static int kvm_set_wallclock(unsigned long now)
return -1;
static cycle_t kvm_clock_read(void)
struct pvclock_vcpu_time_info *src;
cycle_t ret;
src = &get_cpu_var(hv_clock);
ret = pvclock_clocksource_read(src);
return ret;
static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
return kvm_clock_read();
* If we don't do that, there is the possibility that the guest
* will calibrate under heavy load - thus, getting a lower lpj -
* and execute the delays themselves without load. This is wrong,
* because no delay loop can finish beforehand.
* Any heuristics is subject to fail, because ultimately, a large
* poll of guests can be running and trouble each other. So we preset
* lpj here
static unsigned long kvm_get_tsc_khz(void)
struct pvclock_vcpu_time_info *src;
src = &per_cpu(hv_clock, 0);
return pvclock_tsc_khz(src);
static void kvm_get_preset_lpj(void)
unsigned long khz;
u64 lpj;
khz = kvm_get_tsc_khz();
lpj = ((u64)khz * 1000);
do_div(lpj, HZ);
preset_lpj = lpj;
static struct clocksource kvm_clock = {
.name = "kvm-clock",
.read = kvm_clock_get_cycles,
.rating = 400,
int kvm_register_clock(char *txt)
int cpu = smp_processor_id();
int low, high, ret;
low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
ret = native_write_msr_safe(msr_kvm_system_time, low, high);
printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
cpu, high, low, txt);
return ret;
static void __cpuinit kvm_setup_secondary_clock(void)
* Now that the first cpu already had this clocksource initialized,
* we shouldn't fail.
WARN_ON(kvm_register_clock("secondary cpu clock"));
/* ok, done with our trickery, call native */
* After the clock is registered, the host will keep writing to the
* registered memory location. If the guest happens to shutdown, this memory
* won't be valid. In cases like kexec, in which you install a new kernel, this
* means a random memory location will be kept being written. So before any
* kind of shutdown from our side, we unregister the clock by writting anything
* that does not have the 'enable' bit set in the msr
static void kvm_crash_shutdown(struct pt_regs *regs)
native_write_msr(msr_kvm_system_time, 0, 0);
static void kvm_shutdown(void)
native_write_msr(msr_kvm_system_time, 0, 0);
void __init kvmclock_init(void)
if (!kvm_para_available())
if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
msr_kvm_system_time, msr_kvm_wall_clock);
if (kvm_register_clock("boot clock"))
pv_time_ops.sched_clock = kvm_clock_read;
x86_platform.calibrate_tsc = kvm_get_tsc_khz;
x86_platform.get_wallclock = kvm_get_wallclock;
x86_platform.set_wallclock = kvm_set_wallclock;
x86_cpuinit.setup_percpu_clockev =
machine_ops.shutdown = kvm_shutdown;
machine_ops.crash_shutdown = kvm_crash_shutdown;
clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
pv_info.paravirt_enabled = 1; = "KVM";
if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))