Re: [RFC v2 00/18] Refactor configuration of guest memory protection

From: David Gibson <david@gibson.dropbear.id.au>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
	qemu-devel@nongnu.org, brijesh.singh@amd.com,
	frankja@linux.ibm.com, pair@us.ibm.com, qemu-ppc@nongnu.org,
	kvm@vger.kernel.org, mdroth@linux.vnet.ibm.com,
	cohuck@redhat.com, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Richard Henderson <rth@twiddle.net>,
	Eduardo Habkost <ehabkost@redhat.com>
Subject: Re: [RFC v2 00/18] Refactor configuration of guest memory protection
Date: Thu, 4 Jun 2020 13:11:29 +1000	[thread overview]
Message-ID: <20200604031129.GB228651@umbus.fritz.box> (raw)
In-Reply-To: <20200601091618.GC2743@work-vm>

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On Mon, Jun 01, 2020 at 10:16:18AM +0100, Dr. David Alan Gilbert wrote:
> * Sean Christopherson (sean.j.christopherson@intel.com) wrote:
> > On Thu, May 21, 2020 at 01:42:46PM +1000, 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
> > > "guest-memory-protection" property pointing to a platform specific
> > > object which configures and manages the specific details.
> > > 
> > > For now this series covers just AMD SEV and POWER PEF.  I'm hoping it
> > > can be extended to cover the Intel and s390 mechanisms as well,
> > > though.
> > > 
> > > Note: I'm using the term "guest memory protection" throughout to refer
> > > to mechanisms like this.  I don't particular like the term, it's both
> > > long and not really precise.  If someone can think of a succinct way
> > > of saying "a means of protecting guest memory from a possibly
> > > compromised hypervisor", I'd be grateful for the suggestion.
> > 
> > Many of the features are also going far beyond just protecting memory, so
> > even the "memory" part feels wrong.  Maybe something like protected-guest
> > or secure-guest?
> > 
> > A little imprecision isn't necessarily a bad thing, e.g. memory-encryption
> > is quite precise, but also wrong once it encompasses anything beyond plain
> > old encryption.
> 
> The common thread I think is 'untrusted host' - but I don't know of a
> better way to describe that.

Hrm..  UntrustedHost? CompromisedHostMitigation? HostTrustMitigation
(that way it has the same abbreviation as hardware transactional
memory for extra confusion)?  HypervisorPowerLimitation?

HostTrustLimitation? "HTL". That's not too bad, actually, I might go
with that unless someone suggests something better.

-- 
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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