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Subject[PATCH 20/40] KVM: kvmtrace: replace get_cycles with ktime_get v3
Date
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.

[avi: avoid ktime_t in public header]

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
include/linux/kvm.h | 6 +++---
virt/kvm/kvm_trace.c | 19 ++++++++++---------
2 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 8a16b08..5d08f11 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -322,12 +322,12 @@ struct kvm_trace_rec {
__u32 vcpu_id;
union {
struct {
- __u64 cycle_u64;
+ __u64 timestamp;
__u32 extra_u32[KVM_TRC_EXTRA_MAX];
- } __attribute__((packed)) cycle;
+ } __attribute__((packed)) timestamp;
struct {
__u32 extra_u32[KVM_TRC_EXTRA_MAX];
- } nocycle;
+ } notimestamp;
} u;
};

diff --git a/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
index 9acb78b..41dcc84 100644
--- a/virt/kvm/kvm_trace.c
+++ b/virt/kvm/kvm_trace.c
@@ -17,6 +17,7 @@
#include <linux/module.h>
#include <linux/relay.h>
#include <linux/debugfs.h>
+#include <linux/ktime.h>

#include <linux/kvm_host.h>

@@ -35,16 +36,16 @@ static struct kvm_trace *kvm_trace;
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 +70,20 @@ static void kvm_add_trace(void *probe_private, void *call_data,
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_to_ns(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);
}

--
1.6.0.1


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