Re: [PATCH v2] x86/acpi/boot: Do not register processors that cannot be onlined for x2apic

Rafael J. Wysocki
2023-01-10T13:04:37Z

On Thu, Jan 5, 2023 at 11:22 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Thu, Jan 05, 2023 at 06:09:59PM +0100, Rafael J. Wysocki wrote:
> > On Thu, Jan 5, 2023 at 5:11 AM Kishon Vijay Abraham I <kvijayab@amd.com> wrote:
> > >
> > > Section 5.2.12.12 Processor Local x2APIC Structure in the ACPI v6.5
> > > spec mandates that both "enabled" and "online capable" Local APIC Flags
> > > should be used to determine if the processor is usable or not.
> > >
> > > However, Linux doesn't use the "online capable" flag for x2APIC to
> > > determine if the processor is usable. As a result, cpu_possible_mask has
> > > incorrect value and results in more memory getting allocated for per_cpu
> > > variables than it is going to be used.
> > >
> > > Make sure Linux parses both "enabled" and "online capable" flags for
> > > x2APIC to correctly determine if the processor is usable.
> > >
> > > Fixes: aa06e20f1be6 ("x86/ACPI: Don't add CPUs that are not online capable")
> > > Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
> > > Reported-by: Leo Duran <leo.duran@amd.com>
> > > Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
> >
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Are you saying, I should take it through tip?

Works for me either way.

Just please let me know if I need to take care of it. :-)