On Tue Mar 17, 2009 at 09:17:21 -0700, Alexander Valitov wrote:
I also have found out that DOUBLE FAULT situation in Fiasco is cured by turning off "Kernel options->Assembler IPC shortcut" Fiasco option. Does someone know that causes the "DOUBLE FAULT"? As seen from maillist archive it is a known problem, but I wonder why is it still not fixed? Let me explain. Menuconfig says that "assembler IPC shortcut" increases performance of short IPC (I guess it is IPC inside of an address space).
Nope, register only IPC is meant here.
It is definitely a good thing and I'd like to have it turned on. But it could causes crash in kernel (potentially also on hardware???). It is definitely a bad thing. The excuses that I see is that fix is really tricky and couldn't be easily implemented or the root of problem is known and it triggers problem ONLY with QEMU.
I basically can only remember seeing this on Qemu and as it does not really matter there it probably does not make much sense in hunting this one, besides that it's a tricky one. It may be different if it happens on real hardware but still the easy work around is just switching it off.
Adam