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r: 98426
b: refs/heads/master
c: f6e16d5
h: refs/heads/master
v: v3
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Gerd Hoffmann authored and Avi Kivity committed Jun 24, 2008
1 parent 20e3ced commit e83900b
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Showing 3 changed files with 35 additions and 57 deletions.
2 changes: 1 addition & 1 deletion [refs]
Original file line number Diff line number Diff line change
@@ -1,2 +1,2 @@
---
refs/heads/master: 50d0a0f987b83a8dadb1134d834e35ec410392b5
refs/heads/master: f6e16d5ad463d15f285666f588cfe49495c692d9
1 change: 1 addition & 0 deletions trunk/arch/x86/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -383,6 +383,7 @@ config VMI
config KVM_CLOCK
bool "KVM paravirtualized clock"
select PARAVIRT
select PARAVIRT_CLOCK
depends on !(X86_VISWS || X86_VOYAGER)
help
Turning on this option will allow you to run a paravirtualized clock
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89 changes: 33 additions & 56 deletions trunk/arch/x86/kernel/kvmclock.c
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@

#include <linux/clocksource.h>
#include <linux/kvm_para.h>
#include <asm/pvclock.h>
#include <asm/arch_hooks.h>
#include <asm/msr.h>
#include <asm/apic.h>
Expand All @@ -36,83 +37,47 @@ static int parse_no_kvmclock(char *arg)
early_param("no-kvmclock", parse_no_kvmclock);

/* The hypervisor will put information about time periodically here */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct kvm_vcpu_time_info, hv_clock);
#define get_clock(cpu, field) per_cpu(hv_clock, cpu).field
static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
static struct pvclock_wall_clock wall_clock;

static inline u64 kvm_get_delta(u64 last_tsc)
{
int cpu = smp_processor_id();
u64 delta = native_read_tsc() - last_tsc;
return (delta * get_clock(cpu, tsc_to_system_mul)) >> KVM_SCALE;
}

static struct kvm_wall_clock wall_clock;
static cycle_t kvm_clock_read(void);
/*
* 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)
{
u32 wc_sec, wc_nsec;
u64 delta;
struct pvclock_vcpu_time_info *vcpu_time;
struct timespec ts;
int version, nsec;
int low, high;

low = (int)__pa(&wall_clock);
high = ((u64)__pa(&wall_clock) >> 32);
native_write_msr(MSR_KVM_WALL_CLOCK, low, high);

delta = kvm_clock_read();
vcpu_time = &get_cpu_var(hv_clock);
pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
put_cpu_var(hv_clock);

native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
do {
version = wall_clock.wc_version;
rmb();
wc_sec = wall_clock.wc_sec;
wc_nsec = wall_clock.wc_nsec;
rmb();
} while ((wall_clock.wc_version != version) || (version & 1));

delta = kvm_clock_read() - delta;
delta += wc_nsec;
nsec = do_div(delta, NSEC_PER_SEC);
set_normalized_timespec(&ts, wc_sec + delta, nsec);
/*
* Of all mechanisms of time adjustment I've tested, this one
* was the champion!
*/
return ts.tv_sec + 1;
return ts.tv_sec;
}

static int kvm_set_wallclock(unsigned long now)
{
return 0;
return -1;
}

/*
* This is our read_clock function. The host puts an tsc timestamp each time
* it updates a new time. Without the tsc adjustment, we can have a situation
* in which a vcpu starts to run earlier (smaller system_time), but probes
* time later (compared to another vcpu), leading to backwards time
*/
static cycle_t kvm_clock_read(void)
{
u64 last_tsc, now;
int cpu;
struct pvclock_vcpu_time_info *src;
cycle_t ret;

preempt_disable();
cpu = smp_processor_id();

last_tsc = get_clock(cpu, tsc_timestamp);
now = get_clock(cpu, system_time);

now += kvm_get_delta(last_tsc);
preempt_enable();

return now;
src = &get_cpu_var(hv_clock);
ret = pvclock_clocksource_read(src);
put_cpu_var(hv_clock);
return ret;
}

static struct clocksource kvm_clock = {
.name = "kvm-clock",
.read = kvm_clock_read,
Expand All @@ -123,13 +88,14 @@ static struct clocksource kvm_clock = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int kvm_register_clock(void)
static int kvm_register_clock(char *txt)
{
int cpu = smp_processor_id();
int low, high;
low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);

printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
cpu, high, low, txt);
return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
}

Expand All @@ -140,12 +106,20 @@ static void kvm_setup_secondary_clock(void)
* Now that the first cpu already had this clocksource initialized,
* we shouldn't fail.
*/
WARN_ON(kvm_register_clock());
WARN_ON(kvm_register_clock("secondary cpu clock"));
/* ok, done with our trickery, call native */
setup_secondary_APIC_clock();
}
#endif

#ifdef CONFIG_SMP
void __init kvm_smp_prepare_boot_cpu(void)
{
WARN_ON(kvm_register_clock("primary cpu clock"));
native_smp_prepare_boot_cpu();
}
#endif

/*
* After the clock is registered, the host will keep writing to the
* registered memory location. If the guest happens to shutdown, this memory
Expand Down Expand Up @@ -174,13 +148,16 @@ void __init kvmclock_init(void)
return;

if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
if (kvm_register_clock())
if (kvm_register_clock("boot clock"))
return;
pv_time_ops.get_wallclock = kvm_get_wallclock;
pv_time_ops.set_wallclock = kvm_set_wallclock;
pv_time_ops.sched_clock = kvm_clock_read;
#ifdef CONFIG_X86_LOCAL_APIC
pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
#endif
#ifdef CONFIG_SMP
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
#endif
machine_ops.shutdown = kvm_shutdown;
#ifdef CONFIG_KEXEC
Expand Down

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