Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set

[Paolo Bonzini]

On 17/06/2016 17:19, Eduardo Habkost wrote:
> > > So, what happens if the guest play tricks in bits 40-45 when QEMU
> > > sets the limit to 40 but we are running in a 46-bit host? Is it
> > > really a problem? I assumed it would be safe.
> > 
> > The guest expects a "reserved bit set" page fault, but doesn't get one.
> 
> Wait, are you talking about migration only, or are you really
> talking about running current QEMU (hardcoded to 40) on a 46-bit
> host? I'm not talking about migration, above.

I'm talking about both. :(

> We really can't emulate a 40-bit machine in a 46-bit host? I
> didn't expect that.

Unfortunately that's the case. :(

Paolo