Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu | Date | Wed, 28 Nov 2007 12:42:22 -0700 |
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Vivek Goyal <vgoyal@redhat.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)?
However things are implemented completely differently now. I don't think the coherent hypertransport domain of AMD processors actually routes ExtINT interrupts to all cpus but instead one (the default route?) is picked.
So I think for the kdump case we pretty much need to use an IOAPIC in virtual wire mode for recent AMD systems.
For current Intel systems I believe either scenario still works.
> Can you print the LAPIC registers (print_local_APIC) during normal boot > and during kdump boot and paste here?
It's worth a look.
I still think we need to just use apic mode at kernel startup, and be done with it.
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