[Xen-devel] Re: [PATCH][RFC] Emulating real mode with x86_emulate

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Andi Kleen wrote:
> > There are some hard problems with migrating into QEMU.  Namely, the code 
> > that QEMU generates isn't SMP safe (atomic instructions lose their 
> > atomicity)
> >     
> I see.
>
> You're worrying that real mode startup trampolines of OS rely 
> on atomic instructions?  I can't think of much other possible real mode
> multi CPU code.
>   
No, that's a concern for using V2E to handle 32 bit code.  The big 
problem for handling real mode code is dealing with synchronization for 
device state.  With the devices split between QEMU and within the 
hypervisor, this becomes even more complicated.
Any of the interesting guests that use big real mode also depend on 
being able to synchronize this device state.
Regards,

Anthony Liguori

> -Andi
>   
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