linux-kernel - Re: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu

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Date:	Fri, 30 Nov 2007 09:35:34 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ben Woodard <woodard@...hat.com>,
	Neil Horman <nhorman@...hat.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...e.de>,
	hbabu@...ibm.com, Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] kexec: force x86_64 arches to boot kdump kernels on
	boot cpu

On Fri, Nov 30, 2007 at 12:59:26AM -0800, Yinghai Lu wrote:
> On Nov 29, 2007 6:54 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> > Ben Woodard <woodard@...hat.com> writes:
> >
> >
> > > Eric W. Biederman wrote:
> > >> Vivek Goyal <vgoyal@...hat.com> writes:
> > >>
> > >>> Ok. Got it. So in this case we route the interrupts directly through LAPIC
> > >>> and put LVT0 in ExtInt mode and IOAPIC is bypassed.
> > >>>
> > >>> I am looking at Intel Multiprocessor specification v1.4 and as per figure
> > >>> 3-3 on page 3-9, 8259 is connected to LINTIN0 line, which in turn is
> > >>> connected to LINTIN0 pin on all processors. If that is the case, even in
> > >>> this mode, all the CPU should see the timer interrupts (which is coming
> > >>> from 8259)?
> > >>
> 
> there is two mode for mcp55. bios should have one option about virtul
> wired to LVT0 of BSP or IOAPIC pin 0.
> or the option like hpet route to ioapic pin 2.
> 

That's interesting. So with BIOS options I can force timer 
interrupts to be routed through IOAPIC? That would enable us to get
timer interrupts on any of the cpus in legacy mode. Ben, can you give it
a try?

> for kdump fix, could enable LVT0 of CPU for kdump and disable that for BSP?

We would not know the crashing cpu in advance hence can't set it. 

Thanks
Vivek
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