Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory

Marc Orr
2022-06-24T17:19:20Z

On Fri, Jun 24, 2022 at 10:10 AM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 6/24/22 10:06, Marc Orr wrote:
> > I think Peter's point is a little more nuanced than that. Once lazy
> > accept goes into the guest firmware -- without the feature negotiation
> > that Peter is suggesting -- cloud providers now have a bookkeeping
> > problem. Which images have kernels that can boot from a guest firmware
> > that doesn't pre-validate all the guest memory?
>
> Hold on a sec though...
>
> Is this a matter of
>
> can boot from a guest firmware that doesn't pre-validate all the
> guest memory?
>
> or
>
> can boot from a guest firmware that doesn't pre-validate all the
> guest memory ... with access to all of that guest's RAM?
>
> In other words, are we talking about "fails to boot" or "can't see all
> the RAM"?

Ah... yeah, you're right, Dave -- I guess it's the latter. The guest
won't have access to all of the memory that the customer is paying
for. But that's still bad. If the customer buys a 96 GB VM and can
only see 4GB because they're kernel doesn't have these patches they're
going to be confused and frustrated.