On Fri, Sep 24, 2010 at 09:54:14AM -0700, Jesse Barnes wrote: > On Tue, 21 Sep 2010 13:54:39 -0400 > Neil Horman <nhorman@xxxxxxxxxxxxx> wrote: > > > A long time ago I worked on a RHEL5 bug in which kdump hung during boot > > on a set of systems. The systems hung because they never received timer > > interrupts during calibrate_delay. These systems also all had Opteron > > processors on a hypertransport bus, bridged to a pci bus via an Nvidia MCP55 > > northbridge chip. AFter much wrangling I managed to learn from Nvidia that they > > have an undocumented register in some versions of that chip which control how > > legacy interrupts are send to the cpu complex when the ioapic isn't active. > > Nvidia defaults this register to only send legacy interrupts to the BSP, so if > > kdump happens to boot on an AP, we never get timer interrupts and boom. I had > > initially used this quirk as a workaround, with my intent being to move apic > > initalization to an earlier point in the boot process, so the setting of the > > register would be irrelevant. Given the work involved in doing that however, > > the fragile nature of the apic initalization code, and the fact that, over the 2 > > years since we found this bug, the MCP55 is the only chip which seems to have > > this issue, I've figure at this point its likely safer to just carry the quirk > > around. By setting the referenced bits in this hidden register, interrupts will > > be broadcast to all cpus when the ioapic isn't active on the above described > > systems. > > > > Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > > Applied to my linux-next branch, thanks. > Thanks! Neil > -- > Jesse Barnes, Intel Open Source Technology Center > > _______________________________________________ > kexec mailing list > kexec@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/kexec -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
