linux-kernel - Re: [RFC][PATCH 5/3] tracing: Add smi counting to HWLAT

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Message-ID: <20160809212558.GJ30192@twins.programming.kicks-ass.net>
Date:	Tue, 9 Aug 2016 23:25:58 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Clark Williams <williams@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jon Masters <jcm@...hat.com>, Daniel Wagner <wagi@...om.org>,
	Carsten Emde <C.Emde@...dl.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [RFC][PATCH 5/3] tracing: Add smi counting to HWLAT

On Tue, Aug 09, 2016 at 02:05:43PM -0400, Steven Rostedt wrote:
> +int arch_smi_count(void)
> +{
> +	unsigned long long count;
> +	int err;
> +
> +	err = rdmsrl_safe(MSR_SMI_COUNT, &count);
> +	if (err)
> +		return 0;

That's really yucky, relying on _safe() to detect availability.

Also, I just found AMD Fam15h has this counter through PMCs (event
0x2b).

> +
> +	return count;
> +}