linux-kernel - Re: [PATCH 6/9] perf, intel: Use GO/HO bits in perf-ctr

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Date:	Mon, 03 Oct 2011 17:06:27 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	joerg.roedel@....com, mingo@...e.hu, a.p.zijlstra@...llo.nl
Subject: Re: [PATCH 6/9] perf, intel: Use GO/HO bits in perf-ctr

On 10/03/2011 03:49 PM, Gleb Natapov wrote:
> Intel does not have guest/host-only bit in perf counters like AMD
> does.  To support GO/HO bits KVM needs to switch EVENTSELn values
> (or PERF_GLOBAL_CTRL if available) at a guest entry. If a counter is
> configured to count only in a guest mode it stays disabled in a host,
> but VMX is configured to switch it to enabled value during guest entry.
>
> This patch adds GO/HO tracking to Intel perf code and provides interface
> for KVM to get a list of MSRs that need to be switched on a guest entry.
>
> Only cpus with architectural PMU (v1 or later) are supported with this
> patch.  To my knowledge there is not p6 models with VMX but without
> architectural PMU and p4 with VMX are rare and the interface is general
> enough to support them if need arise.
>
> +
> +static int core_guest_get_msrs(int cnt, struct perf_guest_switch_msr *arr)
> +{
> +	struct cpu_hw_events *cpuc =&__get_cpu_var(cpu_hw_events);
> +	int idx;
> +
> +	if (cnt<  x86_pmu.num_counters)
> +		return -ENOMEM;
> +
> +	for (idx = 0; idx<  x86_pmu.num_counters; idx++)  {
> +		struct perf_event *event = cpuc->events[idx];
> +
> +		arr[idx].msr = x86_pmu_config_addr(idx);
> +		arr[idx].host = arr[idx].guest = 0;
> +
> +		if (!test_bit(idx, cpuc->active_mask))
> +			continue;
> +
> +		arr[idx].host = arr[idx].guest =
> +				event->hw.config | ARCH_PERFMON_EVENTSEL_ENABLE;
> +
> +		if (event->attr.exclude_host)
> +			arr[idx].host&= ~ARCH_PERFMON_EVENTSEL_ENABLE;
> +		else if (event->attr.exclude_guest)
> +			arr[idx].guest&= ~ARCH_PERFMON_EVENTSEL_ENABLE;
> +	}
> +
> +	return 0;
> +}

Would be better to calculate these when the host msrs are calculated, 
instead of here, every vmentry.


-- 
error compiling committee.c: too many arguments to function

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