Re: [patch] x86: 2.6.31-rc7 crash due to buggy flat_phys_pkg_id

From: Cyrill Gorcunov
Date: Tue Aug 25 2009 - 15:40:26 EST

[Ravikiran G Thirumalai - Tue, Aug 25, 2009 at 12:20:55PM -0700]
| 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:
| And fixes vsmp too.
| >Or perhaps there is an issue in srat numa nodes numbering?
| >
| Don't think so, local apic id has been used for for 'flat' and 'cluster'
| apic (which was used prior to 'flat') for atleast 15 major releases.
| Cyrill/Yinghai, can you test and confirm if the patch attached does not
| regress the 'UP crash case' mentioned in
| commit 2759c3287de27266e06f1f4e82cbd2d65f6a044c please?
| ---

I would like to but I can;t. I don;t even know where were we hanging
at this crash case. I was only reading commit changelog and since
it was said about "not apic bit set" I thought about disabled apic case.

Personally I like much more quirk Yinghai posted which leaves phys id function
_bared_ and simple as it should be :)

And since it's too late before kernel release -- introducing read apic back
seems to be dangerous I suppose: there are a number of configs which could
be having side effect. At moment they are tested _with_ Yinghai patch and
only vSMP is issued. Though the problem need to be investigated more
closely. But I'm not knowing that much in this area.

-- Cyrill
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