Recently a kdump bug was discovered in which a system would hang inside
calibrate_delay during the booting of the kdump kernel. This was caused
by the fact that the jiffies counter was not being incremented during
timer calibration. The root cause of this problem was found to be a
bios misconfiguration of the hypertransport bus. On system affected by
this hang, the bios had assigned APIC ids which used extended apic bits
(more than the nominal 4 bit ids's), but failed to configure bit 17 of
the hypertransport transaction config register, which indicated that the
mask for the destination field of interrupt packets accross the ht bus
(see section 3.3.9 of
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26094.PDF).
If a crash occurs on a cpu with an APIC id that extends beyond 4 bits,
it will not recieve interrupts during the kdump kernel boot, and this
hang will be the result. The fix is to add this patch, whcih add an
early pci quirk check, to forcibly enable this bit in the httcfg
register. This enables all cpus on a system to receive interrupts, and
allows kdump kernel bootup to procede normally.
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
c6b4832432