Re: KVM crash on unusual PM->RM transition

H. Peter Anvin
2009-04-14T15:48:39Z

Avi Kivity wrote:
>>
>> It looks like KVM will simply crash when it runs into a real-mode state
>> it can't approximate with V86 mode. I guess I had the failed notion
>> that it would kick back such "impossible" states to Qemu.
>
> Exactly. There's the emulate_invalid_guest_state module parameter which
> tells kvm to emulate during such state instead. But this will often
> break as programs leave fs and gs in non-v86-mode compliant, requiring
> more of the emulator than it currently provides.
>

Any reason to not make use of Qemu in userspace, rather than relying on
the in-kernel interpreter for these? The kernel interpreter is
obviously The Right Thing to avoid frequent ping-pong into the kernel,
but it seems to me that such a potential "long-term" situation might be
better handled by Qemu?