[RFC v2 5/7] kvm steal time implementation

Glauber Costa
2010-08-30T16:23:58Z

This is the proposed kvm-side steal time implementation.
It is migration safe, as it checks flags at every read.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
arch/x86/kernel/kvmclock.c | 35 +++++++++++++++++++++++++++++++++++
1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index eb9b76c..a1f4852 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -18,6 +18,8 @@

#include <linux/clocksource.h>
#include <linux/kvm_para.h>
+#include <linux/kernel_stat.h>
+#include <linux/sched.h>
#include <asm/pvclock.h>
#include <asm/msr.h>
#include <asm/apic.h>
@@ -41,6 +43,7 @@ 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 DEFINE_PER_CPU(u64, steal_info);
static struct pvclock_wall_clock wall_clock;

/*
@@ -82,6 +85,32 @@ static cycle_t kvm_clock_read(void)
return ret;
}

+static DEFINE_PER_CPU(u64, steal_info);
+
+cputime_t kvm_get_steal_time(void)
+{
+ u64 delta = 0;
+ u64 *last_steal_info, this_steal_info;
+ struct pvclock_vcpu_time_info *src;
+
+ src = &get_cpu_var(hv_clock);
+ if (!(src->flags & PVCLOCK_STEAL_BIT))
+ goto out;
+
+ this_steal_info = src->steal_time;
+ put_cpu_var(hv_clock);
+
+ last_steal_info = &get_cpu_var(steal_info);
+
+ delta = this_steal_info - *last_steal_info;
+
+ *last_steal_info = this_steal_info;
+ put_cpu_var(steal_info);
+
+out:
+ return msecs_to_cputime(delta);
+}
+
static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
{
return kvm_clock_read();
@@ -134,6 +163,8 @@ static int kvm_register_clock(char *txt)
printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
cpu, high, low, txt);

+ per_cpu(steal_info, cpu) = 0;
+
return native_write_msr_safe(msr_kvm_system_time, low, high);
}

@@ -218,4 +249,8 @@ void __init kvmclock_init(void)

if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+
+
+ if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STEAL_BIT))
+ hypervisor_steal_time = kvm_get_steal_time;
}
--
1.6.2.2