On Tue, Sep 21, 2010 at 01:54:39PM -0400, Neil Horman 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> FWIW, Acked-by: Simon Horman <horms@xxxxxxxxxxxx> -- 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
