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

[Liang, Kan]

On 2/4/2019 10:44 AM, Peter Zijlstra wrote:
> On Mon, Feb 04, 2019 at 04:38:27PM +0100, Peter Zijlstra wrote:
> > +static const struct x86_cpu_desc isolation_ucodes[] = {
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	 9, 0x0000004e),
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	10, 0x0000004e),
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	11, 0x0000004e),
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	12, 0x0000004e),
>
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	10, 0x0000004e),
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	11, 0x0000004e),
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	12, 0x0000004e),
> > +	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	13, 0x0000004e),
>
> Do we want a special stepping (0 / -1) to be able to denote 'all' ?

Something like as below?
#define X86_STEPPING_ANY	0xff

As my understanding, the microcode version for each stepping is 
independent and irrelevant. The 0x0000004e should be just coincidence.
If so, I don't think X86_STEPPING_ANY is very useful.

Andi, if I'm wrong please correct me.

Thanks,
Kan