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

[Liang, Kan]

On 2/4/2019 11:04 AM, Borislav Petkov wrote:
> On Mon, Feb 04, 2019 at 10:57:32AM -0500, Liang, Kan wrote:
> > 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.
>
> Huh?
>
> Why are we looking at the stepping then?
>
> x86_match_cpu_with_stepping() <---

I mean that the microcode version number is irrelevant between stepping.
Let's use SKL server as an example.
+	INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X,		 3, 0x00000021),
+	INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X,		 4, 0x00000000),

We need the function to check the min microcode version number for each 
stepping.


Thanks,
Kan