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

[Peter Zijlstra]

On Thu, Mar 23, 2017 at 11:25:49AM -0700, kan.liang@xxxxxxxxx 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.