From: Wei Huang <wei@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Subject: Re: [PATCH 1/1] perf/x86: Use KERN_INFO when checking PMU fails on virtual environment
Date: Mon, 29 Sep 2014 23:19:23 -0500 [thread overview]
Message-ID: <542A2F4B.5060405@redhat.com> (raw)
In-Reply-To: <1411617314-24659-1-git-send-email-wei@redhat.com>
Hi Ingo, tglx and hpa,
Any comment on this patch? Thanks.
-Wei
On 09/24/2014 10:55 PM, Wei Huang wrote:
> PMU checking can fail due to various reasons. On native machine,
> this is mostly caused by faulty hardware and it is reasonable to
> use KERN_ERR in reporting. However, when kernel is running on
> virtualized environment, this checking can fail if virtual PMU is
> not supported (e.g. KVM on AMD host). It is annoying to see
> an error message on splash screen, even though we know such failure
> is benign on virtualized environment.
>
> This patch checks if kernel is running in virtualized environment.
> If so, it will use KERN_INFO in reporting. This patch was tested
> successfully on KVM.
>
> Signed-off-by: Wei Huang <wei@redhat.com>
> ---
> arch/x86/kernel/cpu/perf_event.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> index 918d75f..16c7302 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -243,7 +243,8 @@ static bool check_hw_exists(void)
>
> msr_fail:
> printk(KERN_CONT "Broken PMU hardware detected, using software events only.\n");
> - printk(KERN_ERR "Failed to access perfctr msr (MSR %x is %Lx)\n", reg, val_new);
> + printk(boot_cpu_has(X86_FEATURE_HYPERVISOR) ? KERN_INFO : KERN_ERR
> + "Failed to access perfctr msr (MSR %x is %Lx)\n", reg, val_new);
>
> return false;
> }
>
next prev parent reply other threads:[~2014-09-30 4:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-25 3:55 [PATCH 1/1] perf/x86: Use KERN_INFO when checking PMU fails on virtual environment Wei Huang
2014-09-30 4:19 ` Wei Huang [this message]
2014-10-03 5:28 ` [tip:perf/core] perf/x86: Tone down kernel messages when the PMU check fails in a " tip-bot for Wei Huang
2014-10-06 21:10 ` Andy Lutomirski
2014-10-07 12:47 ` Peter Zijlstra
2014-10-28 11:08 ` [tip:perf/urgent] perf: Fix bogus kernel printk tip-bot for Peter Zijlstra (Intel)
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