Re: [PATCH 1/2] x86/topology: Name the AMD core-type values

[Pawan Gupta]

On Mon, Jul 06, 2026 at 05:47:13PM -0700, Borislav Petkov wrote:
> On Mon, Jul 06, 2026 at 11:29:07AM -0700, Pawan Gupta wrote:
> > >  /**
> > >   * x86_match_cpu - match current CPU against an array of x86_cpu_ids
> > >   * @match: Pointer to array of x86_cpu_ids. Last entry terminated with
> > > @@ -81,7 +53,7 @@ const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match)
> > >  			continue;
> > >  		if (m->feature != X86_FEATURE_ANY && !cpu_has(c, m->feature))
> > >  			continue;
> > > -		if (!x86_match_vendor_cpu_type(c, m))
> > > +		if (m->type != X86_CPU_TYPE_ANY && c->topo.cpu_type != m->type)
> > 
> > ... matching a hybrid CPU to any cpu_type.
> 
> I don't know what you mean here.

Vulnerability enumeration is done on the BSP, for a hybrid system with BSP
as a performance-core, a vulnerability that only affects efficiency-cores
would not be enumerated. So, x86_match_cpu() currently returns a match for
any cpu-type on a hybrid system.

> enum x86_topology_cpu_type {
>    /* X86_CPU_TYPE_ANY */
>    TOPO_CPU_TYPE_ANY = 0,
>    TOPO_CPU_TYPE_PERFORMANCE,
>    TOPO_CPU_TYPE_EFFICIENCY,
>    TOPO_CPU_TYPE_UNKNOWN,
> };
> 
> These are the Linux-specific CPU types and all vendor CPU types will be mapped
> to them. I hope 255 are enough.

255 should be more than enough, but it doesn't take resolve the problem of
matching a hybrid CPU to any cpu_type.

Apart from struct cpuinfo_x86 for each CPU, we have separate boot_cpu_data
for BSP. One possible solution is to set cpu_type to TOPO_CPU_TYPE_ANY in
BSP specific struct for hybrid systems.

For more accurate matching, x86_topology_cpu_type could be a u32 with
bit-fields for each CPU type. And boot_cpu_data can have:

  boot_cpu_data.topo.cpu_type = (TOPO_CPU_TYPE_PERFORMANCE | TOPO_CPU_TYPE_EFFICIENCY | ...)

on a hybrid system. Problem with this approach is, unless secondary CPUs
are brought up, BSP will not know what all cpu-types are present in the
system. Also with bit-fields, possible cpu-types are further limited.

To circumvent this problem, current implementation matches a hybrid CPU
with any cpu_type.

> > Also, I think now cpu_vuln_blacklist[] needs TOPO_CPU_TYPE_EFFICIENCY
> > instead of ATOM.
> > 
> >   VULNBL_INTEL_TYPE(INTEL_ALDERLAKE,                   ATOM,      RFDS | VMSCAPE),
> >   VULNBL_INTEL_STEPS(INTEL_ALDERLAKE,          X86_STEP_MAX,      VMSCAPE),
> >   VULNBL_INTEL_STEPS(INTEL_ALDERLAKE_L,        X86_STEP_MAX,      RFDS | VMSCAPE),
> >   VULNBL_INTEL_TYPE(INTEL_RAPTORLAKE,                  ATOM,      RFDS | VMSCAPE),
> 
> Ack, right, ATOM == EFFICIENCY in Intel-speak, so I'd need to convert those.
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette