[PATCH 3.16 47/47] KVM: x86/vPMU: refine kvm_pmu err msg when event creation failed

[Ben Hutchings]

3.16.76-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Like Xu <like.xu@xxxxxxxxxxxxxxx>

commit 6fc3977ccc5d3c22e851f2dce2d3ce2a0a843842 upstream.

If a perf_event creation fails due to any reason of the host perf
subsystem, it has no chance to log the corresponding event for guest
which may cause abnormal sampling data in guest result. In debug mode,
this message helps to understand the state of vPMC and we may not
limit the number of occurrences but not in a spamming style.

Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/pmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -187,8 +187,8 @@ static void reprogram_counter(struct kvm
 						 intr ? kvm_perf_overflow_intr :
 						 kvm_perf_overflow, pmc);
 	if (IS_ERR(event)) {
-		printk_once("kvm: pmu event creation failed %ld\n",
-				PTR_ERR(event));
+		pr_debug_ratelimited("kvm_pmu: event creation failed %ld for pmc->idx = %d\n",
+			    PTR_ERR(event), pmc->idx);
 		return;
 	}