From: ebiederm@xmission.com (Eric W. Biederman)
To: Neil Horman <nhorman@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>, Ben Woodard <woodard@redhat.com>,
Andi Kleen <andi@firstfloor.org>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
Andi Kleen <ak@suse.de>,
hbabu@us.ibm.com
Subject: Re: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu
Date: Wed, 28 Nov 2007 10:36:12 -0700 [thread overview]
Message-ID: <m1ir3me0hf.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <20071128160206.GA21286@hmsendeavour.rdu.redhat.com> (Neil Horman's message of "Wed, 28 Nov 2007 11:02:06 -0500")
Neil Horman <nhorman@redhat.com> writes:
> On Wed, Nov 28, 2007 at 10:36:49AM -0500, Vivek Goyal wrote:
>> On Tue, Nov 27, 2007 at 03:24:35PM -0800, Ben Woodard wrote:
>> > Andi Kleen wrote:
>> >>> Are we putting the system back in PIC mode or virtual wire mode? I have
>> >>> not seen systems which support PIC mode. All latest systems seems
>> >>> to be having virtual wire mode. I think in case of PIC mode, interrupts
>> >>
>> >> Yes it's probably virtual wire. For real PIC mode we would need really
>> >> old systems without APIC.
>> >>
>> >>> can be delivered to cpu0 only. In virt wire mode, one can program IOAPIC
>> >>> to deliver interrupt to any of the cpus and that's what we have been
>> >>
>> >> The code doesn't try to program anything specific, it just restores the
> state
>> >> that was left over originally by the BIOS.
>> >>
>> >
>> > So if the BIOS originally left the IOAPIC in a state where the timer
>> > interrupts were only going to CPU0 then by restoring that state we could be
>> > bringing this problem upon ourselves when we restore that state.
>> >
>>
>> Hi Ben,
>>
>> Apart from restoring the original state (Bring APICS back to virtual wire
>> mode), we also reprogram IOAPIC so that timer interrupt can go to crashing
>> cpu (and not necessarily cpu0). Look at following code in disable_IO_APIC.
>>
>> entry.dest.physical.physical_dest =
>> GET_APIC_ID(apic_read(APIC_ID));
>>
>> Here we read the apic id of crashing cpu and program IOAPIC accordingly.
>> This will make sure that even in virtual wire mode, timer interrupts
>> will be delivered to crashing cpu APIC.
>>
> Yes, but according to Bens last debug effort, the APIC printout regarding the
> timer setup, indicates that ioapic_i8259.pin == -1, meaning that the 8259 is not
> routed through the ioapic. In those cases, disable_IO_APIC does not take us
> through the path you reference above, and does not revert to virtual wire mode.
> Instead, it simply disables legacy vector 0, which if I understand this
> correctly, simply tells the ioapic to not handle timer interrupts, trusting that
> the 8259 in the system will deliver that interrupt where it needs to be. If the
> 8259 is wired to deliver timer interrupts to cpu0 only, then you get the problem
> that we have, do you?
Exactly.
It is still interesting to test to see what happens if you plugin the
normal values into ioapic_i8259 for .pin and .apic (.pin is 0 or 2 and .apic is 0)
and see what happens.
Having a command line parameter that could do that would be a cheap temporary
solution.
But this is the most likely reason why the timer interrupt is not working.
Eric
next prev parent reply other threads:[~2007-11-28 18:10 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-27 1:47 [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu Neil Horman
2007-11-27 4:12 ` Eric W. Biederman
2007-11-27 13:13 ` Neil Horman
2007-11-27 13:28 ` Eric W. Biederman
2007-11-27 13:45 ` Andi Kleen
2007-11-27 14:28 ` Neil Horman
2007-11-27 14:43 ` Andi Kleen
2007-11-27 14:48 ` Neil Horman
2007-11-27 15:24 ` Andi Kleen
2007-11-27 15:30 ` Eric W. Biederman
2007-11-27 16:45 ` Neil Horman
2007-11-27 20:50 ` Ben Woodard
2007-11-27 21:05 ` Neil Horman
2007-11-27 22:38 ` Eric W. Biederman
2007-11-27 23:15 ` Ben Woodard
2007-11-28 0:15 ` Eric W. Biederman
2007-11-27 23:40 ` Neil Horman
2007-11-28 0:43 ` Eric W. Biederman
2007-11-28 15:54 ` Neil Horman
2007-11-27 14:56 ` Eric W. Biederman
2007-11-27 15:34 ` Neil Horman
2007-11-27 18:41 ` Ben Woodard
2007-11-27 19:42 ` Neil Horman
2007-11-27 20:00 ` Vivek Goyal
2007-11-27 20:52 ` Neil Horman
2007-11-27 22:24 ` Andi Kleen
2007-11-27 23:24 ` Ben Woodard
2007-11-27 23:56 ` Andi Kleen
2007-11-28 15:36 ` Vivek Goyal
2007-11-28 16:02 ` Neil Horman
2007-11-28 17:36 ` Eric W. Biederman [this message]
2007-11-28 18:16 ` Neil Horman
2007-11-28 19:05 ` Vivek Goyal
2007-11-28 19:42 ` Eric W. Biederman
2007-11-28 21:09 ` Neil Horman
2007-11-28 23:27 ` Eric W. Biederman
2007-11-30 2:16 ` Ben Woodard
2007-11-30 2:54 ` Eric W. Biederman
2007-11-30 8:59 ` Yinghai Lu
2007-11-30 14:35 ` Vivek Goyal
2007-11-30 14:32 ` Neil Horman
2007-11-30 2:12 ` Ben Woodard
2007-11-30 14:42 ` Vivek Goyal
2007-11-30 14:51 ` Neil Horman
2007-12-06 21:39 ` Neil Horman
2007-12-06 22:11 ` Vivek Goyal
2007-12-07 0:10 ` Neil Horman
2007-12-07 14:39 ` Vivek Goyal
2007-12-07 14:53 ` Neil Horman
2007-12-07 15:16 ` Vivek Goyal
2007-12-07 15:53 ` Neil Horman
2007-12-07 18:46 ` Eric W. Biederman
2007-12-07 0:33 ` Eric W. Biederman
2007-12-07 2:04 ` Neil Horman
2007-12-07 8:50 ` Yinghai Lu
2007-12-07 9:22 ` Yinghai Lu
2007-12-07 14:21 ` Neil Horman
2007-12-07 17:58 ` Neil Horman
2007-12-07 19:19 ` yhlu
2007-12-07 20:13 ` Neil Horman
2007-12-10 15:39 ` Neil Horman
2007-12-10 16:20 ` Vivek Goyal
2007-12-11 1:17 ` Eric W. Biederman
2007-12-11 1:08 ` Eric W. Biederman
2007-12-11 3:43 ` Neil Horman
2007-12-11 4:48 ` Eric W. Biederman
2007-12-11 6:31 ` Yinghai Lu
2007-12-11 14:39 ` Neil Horman
2007-12-11 15:29 ` Eric W. Biederman
2007-12-11 18:00 ` Yinghai Lu
2007-12-11 18:29 ` Neil Horman
2007-12-11 18:45 ` Yinghai Lu
2007-12-11 18:22 ` Neil Horman
2007-12-11 18:46 ` Eric W. Biederman
2007-12-11 19:24 ` Neil Horman
2007-12-11 19:51 ` Yinghai Lu
2007-12-11 20:59 ` Neil Horman
2007-12-12 0:16 ` Ben Woodard
2007-12-12 0:52 ` Neil Horman
2007-12-12 1:07 ` Yinghai Lu
2007-12-12 8:43 ` [PATCH] k8: Enable legacy irqs with extended cpu ids Eric W. Biederman
2007-12-12 14:21 ` [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu Andi Kleen
2007-12-12 15:55 ` Neil Horman
2007-12-12 16:07 ` Andi Kleen
2007-12-12 19:43 ` Eric W. Biederman
2007-12-12 20:22 ` Neil Horman
2007-12-12 21:32 ` Eric W. Biederman
2007-12-13 14:39 ` Neil Horman
2007-12-13 15:16 ` Andi Kleen
2007-12-13 15:32 ` Neil Horman
2007-12-17 11:38 ` Neil Horman
2007-12-18 0:13 ` Eric W. Biederman
2007-12-17 15:16 ` Ingo Molnar
2007-12-17 15:47 ` Neil Horman
2007-12-07 18:36 ` Eric W. Biederman
2007-12-07 18:48 ` Neil Horman
2007-11-27 13:53 ` Neil Horman
2007-11-27 10:55 ` Andi Kleen
2007-11-27 11:19 ` Eric W. Biederman
2007-11-27 13:28 ` Neil Horman
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