linux-kernel - Re: [PATCH] x86: print real IOAPIC version for x86-64

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Date:	Wed, 27 May 2009 10:15:02 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	Naga Chumbalkar <nagananda.chumbalkar@...com>
Cc:	x86@...nel.org, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: print real IOAPIC version for x86-64

On Tue, May 26, 2009 at 2:48 PM, Naga Chumbalkar
<nagananda.chumbalkar@...com> wrote:
> Fix the fact that the IOAPIC version number in the x86_64 code path always
> gets assigned to 0, instead of the correct value.
>
> Before the patch: (from "dmesg" output):
> ACPI: IOAPIC (id[0x08] address[0xfec00000] gsi_base[0])
> IOAPIC[0]: apic_id 8, version 0, address 0xfec00000, GSI 0-23     <---
>
> After the patch:
> ACPI: IOAPIC (id[0x08] address[0xfec00000] gsi_base[0])
> IOAPIC[0]: apic_id 8, version 32, address 0xfec00000, GSI 0-23    <---
>
> History:
> io_apic_get_version() was compiled out of the x86_64 code path in the commit
> f2c2cca3acef8b253a36381d9b469ad4fb08563a:
>
> *************************
> Author: Andi Kleen <ak@...e.de>
> Date:   Tue Sep 26 10:52:37 2006 +0200
>
>    [PATCH] Remove APIC version/cpu capability mpparse checking/printing
>
>    ACPI went to great trouble to get the APIC version and CPU capabilities
>    of different CPUs before passing them to the mpparser. But all
>    that data was used was to print it out.  Actually it even faked some data
>    based on the boot cpu, not on the actual CPU being booted.
>
>    Remove all this code because it's not needed.
>
>    Cc: len.brown@...el.com
>
>    Signed-off-by: Andi Kleen <ak@...e.de>
> *************************
>
> At the time, the IOAPIC version number was deliberately not printed in the
> x86_64 code path. However, after the x86 and x86_64 files were merged, the net
> result is that the IOAPIC version is printed incorrectly in the x86_64 code
> path.
>
> The patch below provides a fix. I have tested it with acpi, and with acpi=off,
> and did not see any problems.
>
> Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@...com>
> Cc: Yinghai Lu <yhlu.kernel@...il.com>

Acked-by: Yinghai Lu <yinghai@...nel.org>
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