linux-kernel - Re: [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI

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Date:   Thu, 23 Mar 2017 21:32:55 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...el.com
Cc:     mingo@...hat.com, acme@...nel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, eranian@...gle.com, jolsa@...nel.org,
        ak@...ux.intel.com
Subject: Re: [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI

On Thu, Mar 23, 2017 at 11:25:49AM -0700, kan.liang@...el.com wrote:
> +	for_each_possible_cpu(cpu) {
> +		rdmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, &debugctlmsr);
> +		if (val)
> +			wrmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, debugctlmsr | DEBUGCTLMSR_FREEZE_WHILE_SMM);
> +		else
> +			wrmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, debugctlmsr & ~DEBUGCTLMSR_FREEZE_WHILE_SMM);
> +	}

No; that's just disgusting. Also {rd,wr}msr_on_cpu() should die, exactly
because people end up writing crap like this.