Re: [PATCH v2] x86/smpboot: Make logical package management more robust

[Boris Ostrovsky]

On 12/12/2016 05:04 AM, Thomas Gleixner wrote:
> The logical package management has several issues:
>
>  - The APIC ids provided by ACPI are not required to be the same as the
>    initial APIC id which can be retrieved by CPUID. The APIC ids provided
>    by ACPI are those which are written by the BIOS into the APIC. The
>    initial id is set by hardware and can not be changed. The hardware
>    provided ids contain the real hardware package information.
>
>    Especially AMD sets the effective APIC id different from the hardware id
>    as they need to reserve space for the IOAPIC ids starting at id 0.
>
>    As a consequence those machines trigger the currently active firmware
>    bug printouts in dmesg, These are obviously wrong.
>
>  - Virtual machines have their own interesting of enumerating APICs and
>    packages which are not reliably covered by the current implementation.
>
> The sizing of the mapping array has been tweaked to be generously large to
> handle systems which provide a wrong core count when HT is disabled so the
> whole magic which checks for space in the physical hotplug case is not
> needed anymore.
>
> Simplify the whole machinery and do the mapping when the CPU starts and the
> CPUID derived physical package information is available. This solves the
> observed problems on AMD machines and works for the virtualization issues
> as well.
>
> Remove the extra call from XEN cpu bringup code as it is not longer
> required.
>
> Fixes: d49597fd3bc7 ("x86/cpu: Deal with broken firmware (VMWare/XEN)")
> Reported-and-tested-by: Borislav Petkov <bp@xxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

For Xen:

Tested-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

(Note that we still have
    [Firmware Bug]: CPU13: APIC id mismatch. Firmware: 0 APIC: d
but that will be fixed in Xen code.)

-boris