Re: Questions about the real mode in kvm/qemu

[Paolo Bonzini]

On 26/09/19 10:59, Maxim Levitsky wrote:
> If you mean to ask if there is a way to let guest access use no
> paging at all, that is access host physical addresses directly, then
> indeed there is no way, since regular non 'unrestricted guest' mode
> required both protected mode and paging, and 'unrestricted guest'
> requires EPT. Academically speaking it is of course possible to
> create paging tables that are 1:1...

Not so academically, it's exactly what KVM does.  However, indeed it
would also be possible to switch out of EPT mode when CR0.PG=0.  I'm not
sure why it was done this way, maybe when the code was written it was
simpler to use the identity map.

Let's see if Avi is listening... :)

Paolo