Subject: Re: [PATCH v8 1/4] perf, kvm/{x86, s390}: Remove dependency on uapi/kvm_perf.h

From: Hemant Kumar <[email-masked]>
Date: Wed, 30 Sep 2015 23:42:05 +0530

Hi,

Thanks for the review.

On 09/28/2015 06:30 PM, Alexander Yarygin wrote:
> Hemant Kumar <[email-masked]> writes:
>
>> Its better to remove the dependency on uapi/kvm_perf.h to allow dynamic
>> discovery of kvm events (if its needed). To do this, some extern
>> variables have been introduced with which we can keep the generic
>> functions generic.
>>
>> Signed-off-by: Hemant Kumar <[email-masked]>
>> ---
>> Changes since v7:
>> - Removed __maybe_unused for some parameters which weren't needed.
>>
>>   tools/perf/arch/s390/util/kvm-stat.c | 10 ++++++++-
>>   tools/perf/arch/x86/util/kvm-stat.c  | 12 ++++++++++-
>>   tools/perf/builtin-kvm.c             | 39 +++++++++++++++++++++++-------------
>>   tools/perf/util/kvm-stat.h           |  3 +++
>>   4 files changed, 48 insertions(+), 16 deletions(-)
> Hello,
>
>
> The patchset doesn't break s390 code (and at least build on x86), but I

Thanks for testing it on s390.

> don't really like some things here (e.g. direct access to
> kvm_events_tp), see below.
>
> Thanks.
>
> CC: David Ahern
>
>> diff --git a/tools/perf/arch/s390/util/kvm-stat.c b/tools/perf/arch/s390/util/kvm-stat.c
>> index a5dbc07..c2acb3e 100644
>> --- a/tools/perf/arch/s390/util/kvm-stat.c
>> +++ b/tools/perf/arch/s390/util/kvm-stat.c
>> @@ -10,7 +10,11 @@
>>    */
>>
>>   #include "../../util/kvm-stat.h"
>> -#include <asm/kvm_perf.h>
>> +#include <asm/sie.h>
>> +
>> +#define DECODE_STR_LEN 40
>> +#define VCPU_ID "id"
>> +#define KVM_EXIT_REASON "icptcode"
>>
> I would probably drop them. There are no users besides newly
> introduced const char *vcpu_id_str and decore_str_len etc anyway.

Right, will drop them.

>>   define_exit_reasons_table(sie_exit_reasons, sie_intercept_code);
>>   define_exit_reasons_table(sie_icpt_insn_codes, icpt_insn_codes);
>> @@ -83,6 +87,10 @@ const char * const kvm_events_tp[] = {
>>   	NULL,
>>   };
>>
>> +const char *vcpu_id_str = VCPU_ID;
>> +const int decode_str_len = DECODE_STR_LEN;
>> +const char *exit_reason_code = KVM_EXIT_REASON;
>> +
>>   struct kvm_reg_events_ops kvm_reg_events_ops[] = {
>>   	{ .name = "vmexit", .ops = &exit_events },
>>   	{ NULL, NULL },
>> diff --git a/tools/perf/arch/x86/util/kvm-stat.c b/tools/perf/arch/x86/util/kvm-stat.c
>> index 14e4e66..2d0d43b5 100644
>> --- a/tools/perf/arch/x86/util/kvm-stat.c
>> +++ b/tools/perf/arch/x86/util/kvm-stat.c
>> @@ -1,5 +1,11 @@
>>   #include "../../util/kvm-stat.h"
>> -#include <asm/kvm_perf.h>
>> +#include <asm/svm.h>
>> +#include <asm/vmx.h>
>> +#include <asm/kvm.h>
>> +
>> +#define DECODE_STR_LEN 20
>> +#define VCPU_ID "vcpu_id"
>> +#define KVM_EXIT_REASON "exit_reason"
>>
>>   define_exit_reasons_table(vmx_exit_reasons, VMX_EXIT_REASONS);
>>   define_exit_reasons_table(svm_exit_reasons, SVM_EXIT_REASONS);
>> @@ -129,6 +135,10 @@ const char * const kvm_events_tp[] = {
>>   	NULL,
>>   };
>>
>> +const char *vcpu_id_str = VCPU_ID;
>> +const int decode_str_len = DECODE_STR_LEN;
>> +const char *exit_reason_code = KVM_EXIT_REASON;
>> +
>>   struct kvm_reg_events_ops kvm_reg_events_ops[] = {
>>   	{ .name = "vmexit", .ops = &exit_events },
>>   	{ .name = "mmio", .ops = &mmio_events },
>> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
>> index fc1cffb..ef25fcf 100644
>> --- a/tools/perf/builtin-kvm.c
>> +++ b/tools/perf/builtin-kvm.c
>> @@ -31,20 +31,18 @@
>>   #include <math.h>
>>
>>   #ifdef HAVE_KVM_STAT_SUPPORT
>> -#include <asm/kvm_perf.h>
>>   #include "util/kvm-stat.h"
>>
>> -void exit_event_get_key(struct perf_evsel *evsel,
>> -			struct perf_sample *sample,
>> +void exit_event_get_key(struct perf_evsel *evsel, struct perf_sample *sample,
>>   			struct event_key *key)
>>   {
>>   	key->info = 0;
>> -	key->key = perf_evsel__intval(evsel, sample, KVM_EXIT_REASON);
>> +	key->key = perf_evsel__intval(evsel, sample, exit_reason_code);
>>   }
>>
>>   bool kvm_exit_event(struct perf_evsel *evsel)
>>   {
>> -	return !strcmp(evsel->name, KVM_EXIT_TRACE);
>> +	return !strncmp(evsel->name, kvm_events_tp[1], strlen(evsel->name));
>>   }
> Hmm, direct access to kvm_events_tp? Maybe add a getter for this or
> something like extern char *kvm_exit_trace;?

Makes sense, will make them extern const kvm_{exit,entry}_trace and
assign them in their respective archs.

> /* why strncmp? */
>
>>   bool exit_event_begin(struct perf_evsel *evsel,
>> @@ -60,7 +58,7 @@ bool exit_event_begin(struct perf_evsel *evsel,
>>
>>   bool kvm_entry_event(struct perf_evsel *evsel)
>>   {
>> -	return !strcmp(evsel->name, KVM_ENTRY_TRACE);
>> +	return !strncmp(evsel->name, kvm_events_tp[0], strlen(evsel->name));
>>   }
>>
>>   bool exit_event_end(struct perf_evsel *evsel,
>> @@ -71,8 +69,8 @@ bool exit_event_end(struct perf_evsel *evsel,
>>   }
>>
>>   static const char *get_exit_reason(struct perf_kvm_stat *kvm,
>> -				   struct exit_reasons_table *tbl,
>> -				   u64 exit_code)
>> +			    struct exit_reasons_table *tbl,
>> +			    u64 exit_code)
>>   {
>>   	while (tbl->reason != NULL) {
>>   		if (tbl->exit_code == exit_code)
>> @@ -92,7 +90,7 @@ void exit_event_decode_key(struct perf_kvm_stat *kvm,
>>   	const char *exit_reason = get_exit_reason(kvm, key->exit_reasons,
>>   						  key->key);
>>
>> -	scnprintf(decode, DECODE_STR_LEN, "%s", exit_reason);
>> +	scnprintf(decode, decode_str_len, "%s", exit_reason);
>>   }
>>
>>   static bool register_kvm_events_ops(struct perf_kvm_stat *kvm)
>> @@ -358,7 +356,12 @@ 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[DECODE_STR_LEN];
>> +		char *decode = zalloc(decode_str_len);
>> +
>> +		if (!decode) {
>> +			pr_err("Not enough memory\n");
>> +			return false;
>> +		}
> I think char decode[decode_str_len]; should work or we can allocate this
> once globally (e.g. put it into struct perf_kvm_stat)? Not sure.
>
>>   		kvm->events_ops->decode_key(kvm, &event->key, decode);
>>   		if (!skip_event(decode)) {
>> @@ -366,6 +369,7 @@ static bool handle_end_event(struct perf_kvm_stat *kvm,
>>   				 sample->time, sample->pid, vcpu_record->vcpu_id,
>>   				 decode, time_diff/1000);
>>   		}
>> +		free(decode);
>>   	}
>>
>>   	return update_kvm_event(event, vcpu, time_diff);
>> @@ -386,7 +390,8 @@ struct vcpu_event_record *per_vcpu_record(struct thread *thread,
>>   			return NULL;
>>   		}
>>
>> -		vcpu_record->vcpu_id = perf_evsel__intval(evsel, sample, VCPU_ID);
>> +		vcpu_record->vcpu_id = perf_evsel__intval(evsel, sample,
>> +							  vcpu_id_str);
>>   		thread__set_priv(thread, vcpu_record);
>>   	}
>>
>> @@ -575,7 +580,7 @@ static void show_timeofday(void)
>>
>>   static void print_result(struct perf_kvm_stat *kvm)
>>   {
>> -	char decode[DECODE_STR_LEN];
>> +	char *decode;
>>   	struct kvm_event *event;
>>   	int vcpu = kvm->trace_vcpu;
>>
>> @@ -584,9 +589,14 @@ static void print_result(struct perf_kvm_stat *kvm)
>>   		show_timeofday();
>>   	}
>>
>> +	decode = zalloc(decode_str_len);
>> +	if (!decode) {
>> +		pr_err("Not enough memory\n");
>> +		return;
>> +	}
>>   	pr_info("\n\n");
>>   	print_vcpu_info(kvm);
>> -	pr_info("%*s ", DECODE_STR_LEN, kvm->events_ops->name);
>> +	pr_info("%*s ", decode_str_len, kvm->events_ops->name);
>>   	pr_info("%10s ", "Samples");
>>   	pr_info("%9s ", "Samples%");
>>
>> @@ -605,7 +615,7 @@ static void print_result(struct perf_kvm_stat *kvm)
>>   		min = get_event_min(event, vcpu);
>>
>>   		kvm->events_ops->decode_key(kvm, &event->key, decode);
>> -		pr_info("%*s ", DECODE_STR_LEN, decode);
>> +		pr_info("%*s ", decode_str_len, decode);
>>   		pr_info("%10llu ", (unsigned long long)ecount);
>>   		pr_info("%8.2f%% ", (double)ecount / kvm->total_count * 100);
>>   		pr_info("%8.2f%% ", (double)etime / kvm->total_time * 100);
>> @@ -615,6 +625,7 @@ static void print_result(struct perf_kvm_stat *kvm)
>>   			kvm_event_rel_stddev(vcpu, event));
>>   		pr_info("\n");
>>   	}
>> +	free(decode);
>>
>>   	pr_info("\nTotal Samples:%" PRIu64 ", Total events handled time:%.2fus.\n\n",
>>   		kvm->total_count, kvm->total_time / 1e3);
>> diff --git a/tools/perf/util/kvm-stat.h b/tools/perf/util/kvm-stat.h
>> index ae825d4..59ed51c 100644
>> --- a/tools/perf/util/kvm-stat.h
>> +++ b/tools/perf/util/kvm-stat.h
>> @@ -136,5 +136,8 @@ int cpu_isa_init(struct perf_kvm_stat *kvm, const char *cpuid);
>>   extern const char * const kvm_events_tp[];
>>   extern struct kvm_reg_events_ops kvm_reg_events_ops[];
>>   extern const char * const kvm_skip_events[];
>> +extern const char *vcpu_id_str;
>> +extern const int decode_str_len;
>> +extern const char *exit_reason_code;
>>
>>   #endif /* __PERF_KVM_STAT_H */

-- 
Thanks,
Hemant Kumar