[PATCH] KVM: arm/arm64: Output Guest cntvoff value

[PATCH] KVM: arm/arm64: Output Guest cntvoff value

[amittomer25]

From: Amit Tomar <amittomer25@gmail.com>

This provides an easy access to guest's CVTVOFF value, somewhat
similar to how x86 outputs TSC offset value.

Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>
---
 virt/kvm/arm/arch_timer.c |    1 +
 virt/kvm/arm/trace.h      |   15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 69bca18..b0800fe 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -466,4 +466,5 @@ void kvm_timer_enable(struct kvm *kvm)
 void kvm_timer_init(struct kvm *kvm)
 {
 	kvm->arch.timer.cntvoff = kvm_phys_timer_read();
+	trace_kvm_timer_init(kvm->arch.timer.cntvoff);
 }
diff --git a/virt/kvm/arm/trace.h b/virt/kvm/arm/trace.h
index 37d8b98..c7e1c2f 100644
--- a/virt/kvm/arm/trace.h
+++ b/virt/kvm/arm/trace.h
@@ -52,6 +52,21 @@ TRACE_EVENT(kvm_timer_update_irq,
 		  __entry->vcpu_id, __entry->irq, __entry->level)
 );
 
+TRACE_EVENT(kvm_timer_init,
+	TP_PROTO(unsigned long long cntvoff),
+	TP_ARGS(cntvoff),
+
+	TP_STRUCT__entry(
+		__field(	unsigned long long, cntvoff)
+	),
+
+	TP_fast_assign(
+		__entry->cntvoff	= cntvoff;
+	),
+
+	TP_printk("CNTVOFF: %llx", __entry->cntvoff)
+);
+
 #endif /* _TRACE_KVM_H */
 
 #undef TRACE_INCLUDE_PATH
-- 
1.7.9.5

Re: [PATCH] KVM: arm/arm64: Output Guest cntvoff value

[Christoffer Dall]

On Sat, Jan 02, 2016 at 12:28:29AM +0530, amittomer25@gmail.com wrote:
> From: Amit Tomar <amittomer25@gmail.com>
> 
> This provides an easy access to guest's CVTVOFF value, somewhat
> similar to how x86 outputs TSC offset value.
> 
> Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>

Out of curiosity, what is the value of having this?

Thanks,
-Christoffer

Re: [PATCH] KVM: arm/arm64: Output Guest cntvoff value

[Amit Tomer]

> Out of curiosity, what is the value of having this?

As we know that host and guest clocks are not in sync(Running at a
difference of CNTVOFF value initialized in guest). This value can be
used to correlate the trace event between host and guest.

Thanks,
Amit.

Re: [PATCH] KVM: arm/arm64: Output Guest cntvoff value

[Christoffer Dall]

On Sun, Jan 10, 2016 at 10:55:32PM +0530, Amit Tomer wrote:
> > Out of curiosity, what is the value of having this?
> 
> As we know that host and guest clocks are not in sync(Running at a
> difference of CNTVOFF value initialized in guest). This value can be
> used to correlate the trace event between host and guest.
> 
ok, I'm fine with this patch.

-Christoffer

Re: [PATCH] KVM: arm/arm64: Output Guest cntvoff value

[Amit Tomer]

> ok, I'm fine with this patch.

ok, Thanks.