Re: [PATCH] x86/cpuid: Deal with broken firmware once more

[Charles (Chas) Williams]

On 11/09/2016 11:03 AM, Peter Zijlstra wrote:
> On Wed, Nov 09, 2016 at 04:35:51PM +0100, Thomas Gleixner wrote:
> > Both ACPI and MP specifications require that the APIC id in the respective
> > tables must be the same as the APIC id in CPUID.
> >
> > The kernel retrieves the physical package id from the APIC id during the
> > ACPI/MP table scan and builds the physical to logical package map.
> >
> > There exist Virtualbox and Xen implementations which violate the spec. As a
>
> ISTR it was VMware, not VirtualBox, but whatever.. they're both crazy
> virt stuff.

Yes, this was VMware in particular.  It would be good to get this comment
right so as not to mislead anyone.

> >  /*
> > + * The physical to logical package id mapping is initialized from the
> > + * acpi/mptables information. Make sure that CPUID actually agrees with
> > + * that.
> > + */
> > +static void sanitize_package_id(struct cpuinfo_x86 *c)
> > +{
> > +#ifdef CONFIG_SMP
> > +	unsigned int pkg, apicid, cpu = smp_processor_id();
> > +
> > +	apicid = apic->cpu_present_to_apicid(cpu);
> > +	pkg = apicid >> boot_cpu_data.x86_coreid_bits;
> > +
> > +	if (apicid != c->initial_apicid) {
> > +		pr_err(FW_BUG "CPU%u: APIC id mismatch. Firmware: %x CPUID: %x\n",
> > +		       cpu, apicid, c->initial_apicid);
>
> Should we not also 'fix' c->initial_apicid ?

Since we have c->apicid and c->initial_apicid it seems reasonable to keep one
set to the "correct" value.  I don't think c->initial_apicid is used past
this.

I should have some tests on this patch later today.