H. Peter Anvin wrote: > Just for fun, I tried to boot OS/2 Warp 4.0 under KVM (KVM-59 with the > latest git kernel from Linus as of yesterday, slightly post 2.6.24-rc8.) > I found that it crashes very early, apparently because KVM doesn't > handle an #UD received in user mode. It appears that OS/2 actually > provokes an #UD deliberately in real mode, from the disassembly it looks > like it's trying to probe for the 486 version of cmpxchg (which has a > different opcode than the 586+ version.) >
Strange, the manual lists 0f b0 and 0f b1 as compatible all the way back to the 486. What opcode are you seeing? > It looks like the kernel code filters out a very small number of > real-mode exceptions, and does a KVM exit for all the other ones; the > userspace code then unconditionally barfs. This is presumably a > temporary hack; what is the intended behaviour - for this to be handled > in-kernel, or in userspace? > In kernel. I've never seen a #UD in real mode, that's why it isn't handled. -- Any sufficiently difficult bug is indistinguishable from a feature. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
