From: Bandan Das <bsd@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>,
linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] perf/x86: descriptive failure messages for PMU init
Date: Mon, 15 Apr 2019 08:42:04 -0400 [thread overview]
Message-ID: <jpgo9571lur.fsf@linux.bootlegged.copy> (raw)
In-Reply-To: <20190415120444.GN11158@hirez.programming.kicks-ass.net> (Peter Zijlstra's message of "Mon, 15 Apr 2019 14:04:44 +0200")
Hi Peter,
Peter Zijlstra <peterz@infradead.org> writes:
> On Fri, Apr 12, 2019 at 03:09:17PM -0400, Bandan Das wrote:
>>
>> There's a default warning message that gets printed, however,
>> there are various failure conditions:
>> - a msr read can fail
>> - a msr write can fail
>> - a msr has an unexpected value
>> - all msrs have unexpected values (disable PMU)
>>
>> Also, commit commit 005bd0077a79 ("perf/x86: Modify error message in
>> virtualized environment") completely removed printing the msr in
>> question but these messages could be helpful for debugging vPMUs as
>> well. Add them back and change them to pr_debugs, this keeps the
>> behavior the same for baremetal.
>>
>> Lastly, use %llx to silence checkpatch
>
> Yuck... if you're debugging a hypervisor, you can bloody well run your
> own kernel with additional print slattered around.
>
> The whole make an exception for virt bullshit was already pushing it,
> this is just insane.
>
The only virt specific parts are the pr_debugs which I can remove and
replace with unconditional pr_err()s as suggested by Jiri. Is that ok ?
Bandan
>> @@ -266,12 +282,30 @@ static bool check_hw_exists(void)
>> return true;
>>
>> msr_fail:
>> - if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
>> + if (virt)
>> pr_cont("PMU not available due to virtualization, using software events only.\n");
>> - } else {
>> - pr_cont("Broken PMU hardware detected, using software events only.\n");
>> - pr_err("Failed to access perfctr msr (MSR %x is %Lx)\n",
>> - reg, val_new);
>> + switch (status) {
>> + case READ_FAIL:
>> + if (virt)
>> + pr_debug("Failed to read perfctr msr (MSR %x)\n", reg);
>> + else
>> + pr_err("Failed to read perfctr msr (MSR %x)\n", reg);
>> + break;
>> + case WRITE_FAIL:
>> + if (virt)
>> + pr_debug("Failed to write perfctr msr (MSR %x, wrote: %llx, read: %llx)\n",
>> + reg, val, val_new);
>> + else
>> + pr_err("Failed to write perfctr msr (MSR %x, wrote: %llx, read: %llx)\n",
>> + reg, val, val_new);
>> + break;
>> + case PMU_FAIL:
>> + /* fall through for default message */
>> + default:
>> + if (virt)
>> + pr_debug("Broken PMU hardware detected, using software events only.\n");
>> + else
>> + pr_cont("Broken PMU hardware detected, using software events only.\n");
>> }
prev parent reply other threads:[~2019-04-15 12:42 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-12 19:09 [PATCH] perf/x86: descriptive failure messages for PMU init Bandan Das
2019-04-15 9:48 ` Jiri Olsa
2019-04-15 12:04 ` Peter Zijlstra
2019-04-15 12:42 ` Bandan Das [this message]
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