linux-kernel - Re: [PATCH] x86: do_boot_cpu - check for ESR apic register presence before touching

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Date:	Mon, 15 Sep 2008 09:25:14 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Cyrill Gorcunov" <gorcunov@...il.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: do_boot_cpu - check for ESR apic register presence before touching

On Mon, Sep 15, 2008 at 9:22 AM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> [Yinghai Lu - Mon, Sep 15, 2008 at 09:12:37AM -0700]
> | On Mon, Sep 15, 2008 at 8:05 AM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> | > We should check first if there is ESR register before read/write it.
> | >
> | > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
> | > ---
> | >
> | > Please review and test if possible. Thanks.
> | >
> | > Index: linux-2.6.git/arch/x86/kernel/smpboot.c
> | > ===================================================================
> | > --- linux-2.6.git.orig/arch/x86/kernel/smpboot.c        2008-09-14 21:49:36.000000000 +0400
> | > +++ linux-2.6.git/arch/x86/kernel/smpboot.c     2008-09-15 18:30:37.000000000 +0400
> | > @@ -893,8 +893,10 @@ do_rest:
> | >                /*
> | >                 * Be paranoid about clearing APIC errors.
> | >                */
> | > -               apic_write(APIC_ESR, 0);
> | > -               apic_read(APIC_ESR);
> | > +               if (APIC_INTEGRATED(apic_version[phys_apicid])) {
> | > +                       apic_write(APIC_ESR, 0);
> | > +                       apic_read(APIC_ESR);
> | > +               }
> | >        }
> | >
> | >        /*
> | >
> |
> | maybe unrelated. Do we need to keep apic_version array?
> |
> | YH
> |
>
> as I see ACPI/MP parsing code use it - actually I think we could
> bring another variable - but don't think it worth it. Anyway
> we have to get APIC info from these tables and save it somwhere
> maybe in this array or maybe in another variable. Or you mean
> anything else that I missed?

one apic_version or boot_cpu_apic_version could be enough.

YH
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