x86: Remove the PCI reboot method from the default chain
Steve reported a reboot hang and bisected it back to this commit: a4f1987e x86, reboot: Add EFI and CF9 reboot methods into the default list He heroically tested all reboot methods and found the following: reboot=t # triple fault ok reboot=k # keyboard ctrl FAIL reboot=b # BIOS ok reboot=a # ACPI FAIL reboot=e # EFI FAIL [system has no EFI] reboot=p # PCI 0xcf9 FAIL And I think it's pretty obvious that we should only try PCI 0xcf9 as a last resort - if at all. The other observation is that (on this box) we should never try the PCI reboot method, but close with either the 'triple fault' or the 'BIOS' (terminal!) reboot methods. Thirdly, CF9_COND is a total misnomer - it should be something like CF9_SAFE or CF9_CAREFUL, and 'CF9' should be 'CF9_FORCE' ... So this patch fixes the worst problems: - it orders the actual reboot logic to follow the reboot ordering pattern - it was in a pretty random order before for no good reason. - it fixes the CF9 misnomers and uses BOOT_CF9_FORCE and BOOT_CF9_SAFE flags to make the code more obvious. - it tries the BIOS reboot method before the PCI reboot method. (Since 'BIOS' is a terminal reboot method resulting in a hang if it does not work, this is essentially equivalent to removing the PCI reboot method from the default reboot chain.) - just for the miraculous possibility of terminal (resulting in hang) reboot methods of triple fault or BIOS returning without having done their job, there's an ordering between them as well. Reported-and-bisected-and-tested-by: Steven Rostedt <rostedt@goodmis.org> Cc: Li Aubrey <aubrey.li@linux.intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matthew Garrett <mjg59@srcf.ucam.org> Link: http://lkml.kernel.org/r/20140404064120.GB11877@gmail.comSigned-off-by: Ingo Molnar <mingo@kernel.org>
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