Re: [for-6.0 v5 00/13] Generalize memory encryption models

[David Gibson]

On Tue, Dec 08, 2020 at 01:43:08PM +0100, Cornelia Huck wrote:
> On Tue, 8 Dec 2020 13:57:28 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Fri, Dec 04, 2020 at 02:12:29PM +0100, Cornelia Huck wrote:
> > > On Fri, 4 Dec 2020 13:07:27 +0000
> > > "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > >   
> > > > * Cornelia Huck (cohuck@redhat.com) wrote:  
> > > > > On Fri, 4 Dec 2020 09:06:50 +0100
> > > > > Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> > > > >     
> > > > > > On 04.12.20 06:44, David Gibson wrote:    
> > > > > > > A number of hardware platforms are implementing mechanisms 
> > > > > > > whereby the
> > > > > > > hypervisor does not have unfettered access to guest memory, in 
> > > > > > > order
> > > > > > > to mitigate the security impact of a compromised hypervisor.
> > > > > > > 
> > > > > > > AMD's SEV implements this with in-cpu memory encryption, and 
> > > > > > > Intel has
> > > > > > > its own memory encryption mechanism.  POWER has an upcoming 
> > > > > > > mechanism
> > > > > > > to accomplish this in a different way, using a new memory 
> > > > > > > protection
> > > > > > > level plus a small trusted ultravisor.  s390 also has a protected
> > > > > > > execution environment.
> > > > > > > 
> > > > > > > The current code (committed or draft) for these features has each
> > > > > > > platform's version configured entirely differently.  That doesn't 
> > > > > > > seem
> > > > > > > ideal for users, or particularly for management layers.
> > > > > > > 
> > > > > > > AMD SEV introduces a notionally generic machine option
> > > > > > > "machine-encryption", but it doesn't actually cover any cases 
> > > > > > > other
> > > > > > > than SEV.
> > > > > > > 
> > > > > > > This series is a proposal to at least partially unify 
> > > > > > > configuration
> > > > > > > for these mechanisms, by renaming and generalizing AMD's
> > > > > > > "memory-encryption" property.  It is replaced by a
> > > > > > > "securable-guest-memory" property pointing to a platform specific 
> > > > > > >      
> > > > > > 
> > > > > > Can we do "securable-guest" ?
> > > > > > s390x also protects registers and integrity. memory is only one 
> > > > > > piece
> > > > > > of the puzzle and what we protect might differ from platform to 
> > > > > > platform.
> > > > > >     
> > > > > 
> > > > > I agree. Even technologies that currently only do memory encryption 
> > > > > may
> > > > > be enhanced with more protections later.    
> > > > 
> > > > There's already SEV-ES patches onlist for this on the SEV side.
> > > > 
> > > > <sigh on haggling over the name>
> > > > 
> > > > Perhaps 'confidential guest' is actually what we need, since the
> > > > marketing folks seem to have started labelling this whole idea
> > > > 'confidential computing'.  
> > 
> > That's not a bad idea, much as I usually hate marketing terms.  But it
> > does seem to be becoming a general term for this style of thing, and
> > it doesn't overlap too badly with other terms ("secure" and
> > "protected" are also used for hypervisor-from-guest and
> > guest-from-guest protection).
> > 
> > > It's more like a 'possibly confidential guest', though.  
> > 
> > Hmm.  What about "Confidential Guest Facility" or "Confidential Guest
> > Mechanism"?  The implication being that the facility is there, whether
> > or not the guest actually uses it.
> > 
> 
> "Confidential Guest Enablement"? The others generally sound fine to me
> as well, though; not sure if "Facility" might be a bit confusing, as
> that term is already a bit overloaded.

Well, "facility" is a bit overloaded, but IMO "enablement" is even
more so.  I think I'll go with "confidential guest support" in the
next spin.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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