Re: [edk2] [Qemu-devel] [RFC PATCH] Distinguish between reset types

Subject: Re: [edk2] [Qemu-devel] [RFC PATCH] Distinguish between reset types

From: Paolo Bonzini <>

To: David Woodhouse <>

Date: 2013-02-22 02:19:30

Il 21/02/2013 18:12, David Woodhouse ha scritto:
>> > Since
>> > - I like kvm, and
>> > - I cannot easily change my hardware (which doesn't support UG), and
>> > - I prefer to run the RHEL-6 kernel which has "old" KVM,
>> > I depend on David's fix for the PAM registers.
> Which means your suspend/resume is broken. Yay! :)
> Anthony's patchset should hopefully fix that.
> I wonder what it would take to work around the KVM bug in qemu though;
> can we actually *emulate* 16-bit mode instead of using KVM, on the
> kernels where KVM is broken? And then transition back to using KVM when
> we switch to 32-bit or 64-bit mode?

I don't think you want to do that.  It would be really slow, it would
trade some emulation bugs for others, and people who mind security would
not appreciate the additional attack surface of TCG.

(BTW, that's how the very first version of KVM worked.  It didn't use
hardware virtualization at all until entering 64-bit mode, IIRC).

I think we just have to fix it in 1.5, and suggest a newer kernel to
everyone else.


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