Re: [for-6.0 v5 13/13] s390: Recognize securable-guest-memory option

From: David Gibson <david@gibson.dropbear.id.au>
To: Cornelia Huck <cohuck@redhat.com>
Cc: pair@us.ibm.com, pbonzini@redhat.com, frankja@linux.ibm.com,
	brijesh.singh@amd.com, dgilbert@redhat.com,
	qemu-devel@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>,
	qemu-ppc@nongnu.org, rth@twiddle.net, thuth@redhat.com,
	berrange@redhat.com, mdroth@linux.vnet.ibm.com,
	Marcelo Tosatti <mtosatti@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	david@redhat.com,
	Richard Henderson <richard.henderson@linaro.org>,
	borntraeger@de.ibm.com, kvm@vger.kernel.org,
	qemu-s390x@nongnu.org, pasic@linux.ibm.com
Subject: Re: [for-6.0 v5 13/13] s390: Recognize securable-guest-memory option
Date: Thu, 17 Dec 2020 16:54:42 +1100	[thread overview]
Message-ID: <20201217055442.GJ310465@yekko.fritz.box> (raw)
In-Reply-To: <20201215124526.7c33dc8d.cohuck@redhat.com>

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On Tue, Dec 15, 2020 at 12:45:26PM +0100, Cornelia Huck wrote:
> On Fri,  4 Dec 2020 16:44:15 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > At least some s390 cpu models support "Protected Virtualization" (PV),
> > a mechanism to protect guests from eavesdropping by a compromised
> > hypervisor.
> > 
> > This is similar in function to other mechanisms like AMD's SEV and
> > POWER's PEF, which are controlled bythe "securable-guest-memory" machine
> 
> s/bythe/by the/
> 
> > option.  s390 is a slightly special case, because we already supported
> > PV, simply by using a CPU model with the required feature
> > (S390_FEAT_UNPACK).
> > 
> > To integrate this with the option used by other platforms, we
> > implement the following compromise:
> > 
> >  - When the securable-guest-memory option is set, s390 will recognize it,
> >    verify that the CPU can support PV (failing if not) and set virtio
> >    default options necessary for encrypted or protected guests, as on
> >    other platforms.  i.e. if securable-guest-memory is set, we will
> >    either create a guest capable of entering PV mode, or fail outright
> 
> s/outright/outright./
> 
> > 
> >  - If securable-guest-memory is not set, guest's might still be able to
> 
> s/guest's/guests/

All those corrected, thanks.

> >    enter PV mode, if the CPU has the right model.  This may be a
> >    little surprising, but shouldn't actually be harmful.
> > 
> > To start a guest supporting Protected Virtualization using the new
> > option use the command line arguments:
> >     -object s390-pv-guest,id=pv0 -machine securable-guest-memory=pv0
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/s390x/pv.c         | 58 +++++++++++++++++++++++++++++++++++++++++++
> >  include/hw/s390x/pv.h |  1 +
> >  target/s390x/kvm.c    |  3 +++
> >  3 files changed, 62 insertions(+)
> > 
> 
> Modulo any naming changes etc., I think this should work for s390. I
> don't have the hardware to test this, however, and would appreciate
> someone with a PV setup giving this a go.

Makes sense.

-- 
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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