Re: [PATCH 07/14] hw/i386/vmport: Add support for CMD_GETBIOSUUID

[Liran Alon]

On 10/03/2020 11:34, Michael S. Tsirkin wrote:
> On Tue, Mar 10, 2020 at 01:54:04AM +0200, Liran Alon wrote:
> > This is VMware documented functionallity that some guests rely on.
> > Returns the BIOS UUID of the current virtual machine.
> >
> > Reviewed-by: Nikita Leshenko <address@hidden>
> > Signed-off-by: Liran Alon <address@hidden>
> So this at least seems guest-visible.
>
> So I suspect you need to add properties to
> disable this for old machine types, to avoid
> breaking compatibility with live-migration.

It is indeed guest visible.
In theory, you are right that for every guest-visible change, we should 
make sure to expose it to only new machine-types.

However, in this case, I feel it just unnecessary over-complicates the code.
I don't see how a guest which previously failed to use this command, 
will fail because after Live-Migration it could succeed.

If you insist, I will add such functionality. In that case, do you think 
a single flag will suffice for the addition of all new commands
(i.e. "commands-version" that it's number specifies set of commands to 
expose), or you want to have a per-command flag?

-Liran