linux-kernel - Re: [PATCH V6 2/5] perf/x86/kvm: Avoid unnecessary work in guest filtering

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Date:   Mon, 4 Feb 2019 10:39:09 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, tglx@...utronix.de,
        bp@...en8.de, mingo@...hat.com, ak@...ux.intel.com,
        eranian@...gle.com
Subject: Re: [PATCH V6 2/5] perf/x86/kvm: Avoid unnecessary work in guest
 filtering



On 2/4/2019 10:17 AM, Peter Zijlstra wrote:
> On Mon, Feb 04, 2019 at 04:06:23PM +0100, Peter Zijlstra wrote:
>> On Mon, Jan 21, 2019 at 01:42:28PM -0800, kan.liang@...ux.intel.com wrote:
>>
>> So what's wrong with the below?
>>
>> Installing a quirk for
> 
> (typing hard..)
> 
> but what I was going to say is that it seems overkill to sprinkle all
> that stuff around.
> 

The microcode patch for PEBS has been applied for Icelake and future 
platforms.
   - For the platforms before Haswell, there is no microcode patch 
applied. The x86_pmu.pebs_no_isolation should always be 1.
   - Between Haswell and Kabylake, x86_pmu.pebs_no_isolation is decided 
by quirk table.
   - For Icelake and future platforms, the x86_pmu.pebs_no_isolation 
should always be 0.

The patch you proposed in previous Email can work well for the existing 
platforms. But it will be a problem when adding new support. We have to 
always add INTEL_CPU_DESC(INTEL_FAM6_XXX,	X, 0x00000000) for each CPU ID 
and each stepping. That will be a disaster for maintenance.

Thanks,
Kan