Re: [PATCH 2/2] KVM: SVM: Extend host physical APIC ID field to support more than 8-bit

[Suthikulpanit, Suravee]

Paolo,

On 11/17/2021 8:06 PM, Paolo Bonzini wrote:
> On 11/10/21 11:18, Suravee Suthikulpanit wrote:
> > +    if (level_type != 2 || !x2apic_mode) {
> > +        avic_host_physical_id_mask = 0xffULL;
> > +        goto out;
> > +    }
> > +
> > +    core_mask_width = eax & 0xF;
> > +
> > +    max_phys_mask_width = get_count_order(apic_get_max_phys_apicid());
> > +
> > +    /*
> > +     * Sanity check to ensure core_mask_width for a processor does not
> > +     * exceed the calculated mask.
> > +     */
> > +    if (WARN_ON(core_mask_width > max_phys_mask_width))
> > +        return -EINVAL;
>
> Can it just use apic_get_max_phys_apicid() in x2apic mode, and 0xff in !x2apic mode?  I'm not sure why you need to check CPUID[0xb,0x1].

This is mainly for sanity check of the max_physical_apicid (derived from information in ACPI or MP table),
which can be removed if you think not necessary.

Suravee