linux-kernel - Re: [PATCH] x86/smpboot: Make logical package management more robust

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Message-ID: <20161208091346.uzz3ix4hfpvx2bfu@pd.tnic>
Date:   Thu, 8 Dec 2016 10:13:47 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        "Charles (Chas) Williams" <ciwillia@...cade.com>,
        "M. Vefa Bicakci" <m.v.b@...box.com>,
        Alok Kataria <akataria@...are.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH] x86/smpboot: Make logical package management more robust

On Thu, Dec 08, 2016 at 10:04:25AM +0100, 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 way 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.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Already

Tested-by: Borislav Petkov <bp@...e.de>

Thanks!

-- 
Regards/Gruss,
    Boris.

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