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

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Date:	Tue, 27 Nov 2007 08:30:47 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Neil Horman <nhorman@...driver.com>
Cc:	Andi Kleen <ak@...e.de>, Neil Horman <nhorman@...hat.com>,
	hbabu@...ibm.com, vgoyal@...ibm.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu

Neil Horman <nhorman@...driver.com> writes:

> So, it sounds to me then, like unless I'm willing to really re-write the APIC
> setup code (which I don't feel qualified to do quite yet), that the immediate
> solution would be to not rely on interrupts in legacy mode, which was according
> to my understanding, what the use of the irqpoll command line option was
> supposed to enable.  Any thoughts as to why that might not be working in this
> case, or suggested tests to determine a cause there?

Hmm.  It looks like irqpoll expects to have at least one irq working.
I wonder if we can fix that.

Looking at it from the other direction what does this line
from check_timer() look like when you boot a normal kernel?

	apic_printk(APIC_VERBOSE,KERN_INFO "..TIMER: vector=0x%02X apic1=%d pin1=%d apic2=%d pin2=%d\n",
		cfg->vector, apic1, pin1, apic2, pin2);

I'm curious what values we see at boot for the legacy mode the first
time it is setup, and possibly what chipset you are on.
I know we have had a few times where we have failed to reprogram
the ioapic properly at shutdown.  So it can't hurt to look at
that possibility one last time.

For whatever it is worth my original attempt at using only the
apic mode was commit: f2b36db692b7ff6972320ad9839ae656a3b0ee3e
Looks like I didn't have an x86_64 version.

It looks like about half the cleanups I needed was to decouple
smp cpu startup and apic initialization.  I think the hotplug cpu
case has done a more thorough version of that now.

There was a bit of reshuffling needed to get the everything initialized
in the right order when we started apic mode sooner.

Anyway I might just take another look at this if I can find enough
moments to string together.

Eric
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