Re: [RFC PATCH 00/13] Add support for Mirror VM.

[Ashish Kalra]

Hello Paolo,

On Mon, Aug 16, 2021 at 04:58:02PM +0200, Paolo Bonzini wrote:
> On 16/08/21 16:44, Ashish Kalra wrote:
> > I think that once the mirror VM starts booting and running the UEFI
> > code, it might be only during the PEI or DXE phase where it will
> > start actually running the MH code, so mirror VM probably still need
> > to handles KVM_EXIT_IO when SEC phase does I/O, I can see PIC
> > accesses and Debug Agent initialization stuff in SEC startup code.
> 
> That may be a design of the migration helper code that you were working
> with, but it's not necessary.
> 
Actually my comments are about a more generic MH code.

> The migration helper can be just some code that the guest "donates" to
> the host.  The entry point need not be the usual 0xfffffff0; it can be
> booted directly in 64-bit mode with a CR3 and EIP that the guest
> provides to the guest---for example with a UEFI GUIDed structure.

Yes, this is consistent with the MH code we are currently testing, it
boots directly into 64-bit mode. This is what Tobin's response is also
pointing out to.

Thanks,
Ashish
> 
> In fact, the migration helper can run even before the guest has booted
> and while the guest is paused, so I don't think that it is possible to
> make use of any device emulation code in it.
> 
> Paolo
>