linux-kernel - Re: [PATCH] buitin-kvm: Update cmd_kvm() to check perf

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Date: Mon, 27 May 2024 15:12:18 +0900
From: Yunseong Kim <yskelg@...il.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, skhan@...uxfoundation.org,
 Austin Kim <austindh.kim@...il.com>, shjy180909@...il.com,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] buitin-kvm: Update cmd_kvm() to check perf_host value



On 5/23/24 1:23 오후, Namhyung Kim wrote:
> Hello,
> 
> On Wed, May 15, 2024 at 12:54 PM <yskelg@...il.com> wrote:
>>
>> From: Yunseong Kim <yskelg@...il.com>
>>
>> According to perf-kvm.txt, the default operation is --guest, meaning
>> perf_host should be set to false and perf_guest to true. Currently,
>> the incorrect usage of --no-host and --no-guest still results in
>> the default --guest operation.
> 
> Hmm, right.. This is not good.
> 
>>
>> This patch updates the usage messages to include the --no-guest option
>> for those who only want host data, as well as the --no-host and
>> --no-guest case.
> 
> I'm not sure if it's worth mentioning the host-only use case which is
> not expected for this command.  I think it's enough to warn the
> no-host and no-guest use cases.

Thank you Namhyung for the code review!

I wasn't sure if it was necessary to mention that either.

I should have asked in the patch mail first.

>> Signed-off-by: Yunseong Kim <yskelg@...il.com>
>> ---
>>  tools/perf/builtin-kvm.c | 19 +++++++++++++------
>>  1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
>> index 71165036e4ca..654a07658cdd 100644
>> --- a/tools/perf/builtin-kvm.c
>> +++ b/tools/perf/builtin-kvm.c
>> @@ -2129,7 +2129,7 @@ int cmd_kvm(int argc, const char **argv)
>>                 OPT_BOOLEAN(0, "guest", &perf_guest,
>>                             "Collect guest os data"),
>>                 OPT_BOOLEAN(0, "host", &perf_host,
>> -                           "Collect host os data"),
>> +                          "Collect host os data. Host only with --host --no-guest"),
>>                 OPT_STRING(0, "guestmount", &symbol_conf.guestmount, "directory",
>>                            "guest mount directory under which every guest os"
>>                            " instance has a subdir"),
>> @@ -2150,16 +2150,23 @@ int cmd_kvm(int argc, const char **argv)
>>                                                 "buildid-list", "stat", NULL };
>>         const char *kvm_usage[] = { NULL, NULL };
>>
>> -       perf_host  = 0;
>> -       perf_guest = 1;
>> +       /*
>> +        * tools/perf/Documentation/perf-kvm.txt
>> +        *
>> +        *    Default('')         ->  perf.data.guest
>> +        *    --host              ->  perf.data.kvm
>> +        *    --guest             ->  perf.data.guest
>> +        *    --host --guest      ->  perf.data.kvm
>> +        *    --host --no-guest   ->  perf.data.host
>> +        */
>> +       perf_host = false;
>> +       perf_guest = true;
> 
> Probably not needed.

I agree.

>>
>>         argc = parse_options_subcommand(argc, argv, kvm_options, kvm_subcommands, kvm_usage,
>>                                         PARSE_OPT_STOP_AT_NON_OPTION);
>> -       if (!argc)
>> +       if (!argc || (!perf_host && !perf_guest))
>>                 usage_with_options(kvm_usage, kvm_options);
>>
>> -       if (!perf_host)
>> -               perf_guest = 1;
> 
> Instead of showing the whole usage, I think it's better to
> print a specific message for this case.
> 
> Oh, I've realized that we have 'h' modifier for hypervisors
> (on ARM64?)  Then maybe no-host + no-guest is a valid
> combination.  Probably we need to add --hypervisor option
> then.
> 
> Thanks,
> Namhyung

Yes, I have a native Arm64 devlopment environment.

So I'll implement and test it and send the patch.


Thank you so much for the detailed review!


Warm Regards,

Yunseong Kim

>>
>>         if (!file_name) {
>>                 file_name = get_filename_for_perf_kvm();
>> --
>> 2.34.1
>>