[PATCH 2/8] kvmtrace: replace get_cycles with ktime_get v3

[ehrhardt@linux.vnet.ibm.com]

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

The current kvmtrace code uses get_cycles() while the interpretation would be
easier using using nanoseconds. ktime_get() should give at least the same
accuracy as get_cycles on all architectures (even better on 32bit archs) but
at a better unit (e.g. comparable between hosts with different frequencies.

V3 of this patch now uses the ktime_get() as discussed on the mailing list.
This ensures that the granularity is always 64 bit on all architetcures and
in the background getnstimeofday is used giving us ns granularity.
Additionally this gives us only one generic implementation without need for
an arch hook.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
---

[diffstat]
 include/linux/kvm.h  |    6 +++---
 virt/kvm/kvm_trace.c |   18 +++++++++---------
 2 files changed, 12 insertions(+), 12 deletions(-)

[diff]

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -322,12 +322,12 @@
 	__u32 vcpu_id;
 	union {
 		struct {
-			__u64 cycle_u64;
+			ktime_t timestamp;
 			__u32 extra_u32[KVM_TRC_EXTRA_MAX];
-		} cycle;
+		} timestamp;
 		struct {
 			__u32 extra_u32[KVM_TRC_EXTRA_MAX];
-		} nocycle;
+		} notimestamp;
 	} u;
 } __attribute__((packed));
 
diff --git a/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
--- a/virt/kvm/kvm_trace.c
+++ b/virt/kvm/kvm_trace.c
@@ -35,16 +35,16 @@
 struct kvm_trace_probe {
 	const char *name;
 	const char *format;
-	u32 cycle_in;
+	u32 timestamp_in;
 	marker_probe_func *probe_func;
 };
 
-static inline int calc_rec_size(int cycle, int extra)
+static inline int calc_rec_size(int timestamp, int extra)
 {
 	int rec_size = KVM_TRC_HEAD_SIZE;
 
 	rec_size += extra;
-	return cycle ? rec_size += KVM_TRC_CYCLE_SIZE : rec_size;
+	return timestamp ? rec_size += KVM_TRC_CYCLE_SIZE : rec_size;
 }
 
 static void kvm_add_trace(void *probe_private, void *call_data,
@@ -69,20 +69,20 @@
 	WARN_ON(!(extra <= KVM_TRC_EXTRA_MAX));
 	extra 		= min_t(u32, extra, KVM_TRC_EXTRA_MAX);
 
-	rec.rec_val |= TRACE_REC_TCS(p->cycle_in)
+	rec.rec_val |= TRACE_REC_TCS(p->timestamp_in)
 			| TRACE_REC_NUM_DATA_ARGS(extra);
 	
-	if (p->cycle_in) {
-		rec.u.cycle.cycle_u64 = get_cycles();
+	if (p->timestamp_in) {
+		rec.u.timestamp.timestamp = ktime_get();
 
 		for (i = 0; i < extra; i++)
-			rec.u.cycle.extra_u32[i] = va_arg(*args, u32);
+			rec.u.timestamp.extra_u32[i] = va_arg(*args, u32);
 	} else {
 		for (i = 0; i < extra; i++)
-			rec.u.nocycle.extra_u32[i] = va_arg(*args, u32);
+			rec.u.notimestamp.extra_u32[i] = va_arg(*args, u32);
 	}
 
-	size = calc_rec_size(p->cycle_in, extra * sizeof(u32));
+	size = calc_rec_size(p->timestamp_in, extra * sizeof(u32));
 	relay_write(kt->rchan, &rec, size);
 }