[RFC 3/7] measure time out of guest

[Glauber Costa <glommer@redhat.com>]

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              |   12 +++++++++++-
 2 files changed, 13 insertions(+), 1 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 e7e3b50..680feaa 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -925,8 +925,9 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
 	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;
 
+	vcpu->hv_clock.steal_time = vcpu->time_out / 1000000;
 	/*
 	 * The interface expects us to write an even number signaling that the
 	 * update is finished. Since the guest won't see the intermediate
@@ -1798,6 +1799,8 @@ 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())
@@ -1815,12 +1818,19 @@ 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