[RFC 4/8] measure time out of guest

Glauber Costa
2010-08-30T16:23:56Z

By measuring time between a vcpu_put and a vcpu_load, we can
estimate how much time did the guest stay out of the cpu.
This is exported to the guest at every clock update.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/x86.c | 13 +++++++++++--
2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 502e53f..bc28aff 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -364,6 +364,8 @@ struct kvm_vcpu_arch {
u64 hv_vapic;

cpumask_var_t wbinvd_dirty_mask;
+ u64 time_out;
+ u64 last_time_out;
};

struct kvm_arch {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f4b77ea..9d08032 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -906,6 +906,7 @@ static void kvm_write_guest_time(struct kvm_vcpu *v, bool update_time)
if ((!vcpu->time_page))
return;

+ vcpu->hv_clock.steal_time = vcpu->time_out / 1000000;
if (!update_time)
return;

@@ -928,8 +929,7 @@ static void kvm_write_guest_time(struct kvm_vcpu *v, bool update_time)
vcpu->hv_clock.system_time = ts.tv_nsec +
(NSEC_PER_SEC * (u64)ts.tv_sec) + v->kvm->arch.kvmclock_offset;

- vcpu->hv_clock.flags = 0;
-
+ vcpu->hv_clock.flags = PVCLOCK_STEAL_BIT;
/*
* The interface expects us to write an even number signaling that the
* update is finished. Since the guest won't see the intermediate
@@ -1801,6 +1801,8 @@ static bool need_emulate_wbinvd(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
+ s64 now;
+
/* Address WBINVD may be executed by guest */
if (need_emulate_wbinvd(vcpu)) {
if (kvm_x86_ops->has_wbinvd_exit())
@@ -1818,12 +1820,19 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
per_cpu(cpu_tsc_khz, cpu) = khz;
}
kvm_request_guest_time_update(vcpu);
+
+ now = getnsboottime();
+
+ if (vcpu->arch.last_time_out != 0)
+ vcpu->arch.time_out += now - vcpu->arch.last_time_out;
}

void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
kvm_x86_ops->vcpu_put(vcpu);
kvm_put_guest_fpu(vcpu);
+
+ vcpu->arch.last_time_out = getnsboottime();
}

static int is_efer_nx(void)
--
1.6.2.2