linux-kernel - Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg

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Message-ID: <20090825192624.GA12763@elte.hu>
Date:	Tue, 25 Aug 2009 21:26:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Ravikiran G Thirumalai <kiran@...lex86.org>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Yinghai Lu <yinghai@...nel.org>, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org, shai@...lex86.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg_id


* Ravikiran G Thirumalai <kiran@...lex86.org> wrote:

> On Tue, Aug 25, 2009 at 10:31:30PM +0400, Cyrill Gorcunov wrote:
> >[Ingo Molnar - Tue, Aug 25, 2009 at 08:15:00PM +0200]
> >| 
> >
> >I'm definitely not APIC expert but since I was partially involved
> >letme turn in.
> >
> >Original commit which causes problem for vSMP seems to be due
> >to cpu_has_apic bit turned off (ie due to being manually disabled
> >or acpi table broken) so further read apic id will return plain
> >zero (we're talking about 64 bits now). So frnakly I don't understand
> >what is wrong with Ravikiran's patch. In case of apic disabled
> >initial apic value will be used anyway (which is latched but
> >actually may be changed, but it's not our case).
> >
> 
> Exactly my thinking.  I hoped the patch I posted solves both cases --
> does not depend on local apic id for the "fix crash on certain UP configs"
> case in the commit here:
> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=2759c3287de27266e06f1f4e82cbd2d65f6a044c
> 
> And fixes vsmp too.

Sidenote for .32: i am somewhat worried about the spreading of 
various cpu_has_apic checks. We should separate it out more cleanly 
and provide an apic-> callback instead and avoid this ugly flaggery.

	Ingo
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