If two (or more) unknown NMIs arrive on different CPUs, there is a large chance both CPUs will wind up inside panic(). This is fine, unless you want to enter KDB -since now KDB cannot round up all CPUs, because some of them are stuck inside panic_smp_self_stop with NMI latched. This is easy to replicate with QEMU. Boot with -smp 4 and send an untargetted, broadcast NMI using the monitor.
Solution for this is simple - add a new call, try_panic, which will be invoked in cases where some special behavior is desired if someone else is already panicking. For handling unknown NMIs, we now call try_panic instead. If panic() is already active in the system, just exit out of the NMI handler. This lets KDB roundup CPUs.
This affects linux-next.
Tuesday, March 6, 2012
Friday, March 2, 2012
ATAG (P): 0x00000100 Linked (V): 0xff008000 Actual (P): 0x00a00800 Desired (P): 0x00108000 Handing off to C... [XEN] __ __ _____ ___ ____ ____ [XEN] \ \/ /___ _ __ |___ / / _ \ |___ \ |___ \ [XEN] \ // _ \ '_ \ |_ \| | | | __) |__ __) | [XEN] / \ __/ | | | ___) | |_| | / __/|__/ __/ [XEN] /_/\_\___|_| |_| |____(_)___(_)_____| |_____| [XEN] [XEN] Xen/ARMv7 virtual machine monitor for ARM architecture [XEN] Copyright (C) 2012 Andrei Warkentin <email@example.com> [XEN] Copyright (C) 2007 Samsung Electronics Co, Ltd. All Rights Reserved. [XEN] http://www.cl.cam.ac.uk/netos/xen [XEN] University of Cambridge Computer Laboratory [XEN] [XEN] Xen version 3.0.2-2 (andreiw@(none)) (gcc version 4.4.3 (GCC) ) Fri Mar 2 01:59:34 EST 2012 [XEN] Platform: arm-tegra [XEN] GIT SHA: ffd558debcf08dcf59a0c38115906030bf6f261c [XEN] [XEN] TTB PA 0x104000 [XEN] idle_pgd VA 0xff004000 [XEN] xen_pstart 0x0 [XEN] xen_pend 0x40000000 [XEN] _end 0xff03e708 [XEN] _end VA 0x13E708 [XEN] nr_pages needed for all page_infos = 0x500 [XEN] frame table is at 0xff03f000-0xff53f000 [XEN] xenheap_phys_start = 0x648000 (VA 0xff548000) [XEN] xenheap_phys_end = 0x848000 (VA 0xff748000) [XEN] looking at bank 0 [XEN] base - 0x0 [XEN] end - 0x40000000 [XEN] calling init_boot_pages on 0x648000-0x40000000 [XEN] Using scheduler: Simple EDF Scheduler (sedf) [XEN] Initializing ARM FCSE Unit [XEN] *** LOADING DOMAIN : 0 *** [XEN] DOM0 image is not a Xen-compatible Elf image. [XEN] Could not set up DOM0 guest OS [XEN] [XEN] VMM Panic at xensetup.c:357https://github.com/andreiw/xen3-arm-tegra
Hopefully the next time I work on this won't be in another half a year.