Re: [PATCH 08/11] perf kvm: allow for variable string sizes

[David Ahern]

On 5/5/14, 4:27 AM, Christian Borntraeger wrote:
> > diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> > index 922706c..806c0e4 100644
> > --- a/tools/perf/builtin-kvm.c
> > +++ b/tools/perf/builtin-kvm.c
> > @@ -75,7 +75,7 @@ struct kvm_events_ops {
> >   	bool (*is_end_event)(struct perf_evsel *evsel,
> >   			     struct perf_sample *sample, struct event_key *key);
> >   	void (*decode_key)(struct perf_kvm_stat *kvm, struct event_key *key,
> > -			   char decode[20]);
> > +			   char *decode);
> >   	const char *name;
> >   };
> >
> > @@ -84,6 +84,8 @@ struct exit_reasons_table {
> >   	const char *reason;
> >   };
> >
> > +#define DECODE_STR_LEN_MAX 80
> > +
> >   #define EVENTS_BITS		12
> >   #define EVENTS_CACHE_SIZE	(1UL << EVENTS_BITS)
> >
> > @@ -101,6 +103,8 @@ struct perf_kvm_stat {
> >   	struct exit_reasons_table *exit_reasons;
> >   	const char *exit_reasons_isa;
> >
> > +	int decode_str_len;
> > +

This should not be a part of the perf_kvm_stat struct. Just leave it as 
a macro and use DECODE_STR_LEN_MAX in place of 20. Which means 
DECODE_STR_LEN_MAX needs to be 20 in this patch, and arch specific in 
the follow up patch.

> >   	struct kvm_events_ops *events_ops;
> >   	key_cmp_fun compare;
> >   	struct list_head kvm_events_cache[EVENTS_CACHE_SIZE];
> > @@ -182,12 +186,12 @@ static const char *get_exit_reason(struct perf_kvm_stat *kvm,
> >
> >   static void exit_event_decode_key(struct perf_kvm_stat *kvm,
> >   				  struct event_key *key,
> > -				  char decode[20])
> > +				  char *decode)
> >   {
> >   	const char *exit_reason = get_exit_reason(kvm, kvm->exit_reasons,
> >   						  key->key);
> >
> > -	scnprintf(decode, 20, "%s", exit_reason);
> > +	scnprintf(decode, kvm->decode_str_len, "%s", exit_reason);
> >   }
> >
> >   static struct kvm_events_ops exit_events = {
> > @@ -249,10 +253,11 @@ static bool mmio_event_end(struct perf_evsel *evsel, struct perf_sample *sample,
> >
> >   static void mmio_event_decode_key(struct perf_kvm_stat *kvm __maybe_unused,
> >   				  struct event_key *key,
> > -				  char decode[20])
> > +				  char *decode)
> >   {
> > -	scnprintf(decode, 20, "%#lx:%s", (unsigned long)key->key,
> > -				key->info == KVM_TRACE_MMIO_WRITE ? "W" : "R");
> > +	scnprintf(decode, kvm->decode_str_len, "%#lx:%s",
> > +		  (unsigned long)key->key,
> > +		  key->info == KVM_TRACE_MMIO_WRITE ? "W" : "R");
> >   }
> >
> >   static struct kvm_events_ops mmio_events = {
> > @@ -292,10 +297,11 @@ static bool ioport_event_end(struct perf_evsel *evsel,
> >
> >   static void ioport_event_decode_key(struct perf_kvm_stat *kvm __maybe_unused,
> >   				    struct event_key *key,
> > -				    char decode[20])
> > +				    char *decode)
> >   {
> > -	scnprintf(decode, 20, "%#llx:%s", (unsigned long long)key->key,
> > -				key->info ? "POUT" : "PIN");
> > +	scnprintf(decode, kvm->decode_str_len, "%#llx:%s",
> > +		  (unsigned long long)key->key,
> > +		  key->info ? "POUT" : "PIN");
> >   }
> >
> >   static struct kvm_events_ops ioport_events = {
> > @@ -523,13 +529,13 @@ static bool handle_end_event(struct perf_kvm_stat *kvm,
> >   	time_diff = sample->time - time_begin;
> >
> >   	if (kvm->duration && time_diff > kvm->duration) {
> > -		char decode[32];
> > +		char decode[DECODE_STR_LEN_MAX];
> >
> >   		kvm->events_ops->decode_key(kvm, &event->key, decode);
> >   		if (strcmp(decode, "HLT")) {
> > -			pr_info("%" PRIu64 " VM %d, vcpu %d: %s event took %" PRIu64 "usec\n",
> > +			pr_info("%" PRIu64 " VM %d, vcpu %d: %*s event took %" PRIu64 "usec\n",
> >   				 sample->time, sample->pid, vcpu_record->vcpu_id,
> > -				 decode, time_diff/1000);
> > +				 32, decode, time_diff/1000);

This pr_info does not need the length.

David
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