On 08/25/2010 05:43 PM, Glauber Costa wrote:
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@xxxxxxxxxx>
---
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);
+}
Can this be changed to properly deal with overflow in
src->steal_time, the same way we deal with (eg jiffie)
overflow elsewhere in the kernel?
--
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