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

Liang, Kan
2019-02-04T15:39:14Z

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@linux.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