Re: [PATCH v7 10/13] spapr: Add PEF based confidential guest support

David Gibson
2021-01-29T05:09:48Z

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On Fri, Jan 15, 2021 at 04:41:51PM +0100, Cornelia Huck wrote:
> On Thu, 14 Jan 2021 10:58:08 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
>
> > Some upcoming POWER machines have a system called PEF (Protected
> > Execution Facility) which uses a small ultravisor to allow guests to
> > run in a way that they can't be eavesdropped by the hypervisor. The
> > effect is roughly similar to AMD SEV, although the mechanisms are
> > quite different.
> >
> > Most of the work of this is done between the guest, KVM and the
> > ultravisor, with little need for involvement by qemu. However qemu
> > does need to tell KVM to allow secure VMs.
> >
> > Because the availability of secure mode is a guest visible difference
> > which depends on having the right hardware and firmware, we don't
> > enable this by default. In order to run a secure guest you need to
> > create a "pef-guest" object and set the confidential-guest-support
> > property to point to it.
> >
> > Note that this just *allows* secure guests, the architecture of PEF is
> > such that the guest still needs to talk to the ultravisor to enter
> > secure mode. Qemu has no directl way of knowing if the guest is in
> > secure mode, and certainly can't know until well after machine
> > creation time.
> >
> > To start a PEF-capable guest, use the command line options:
> > -object pef-guest,id=pef0 -machine confidential-guest-support=pef0
> >
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> > docs/confidential-guest-support.txt | 3 +
> > docs/papr-pef.txt | 30 +++++++
> > hw/ppc/meson.build | 1 +
> > hw/ppc/pef.c | 119 ++++++++++++++++++++++++++++
> > hw/ppc/spapr.c | 6 ++
> > include/hw/ppc/pef.h | 25 ++++++
> > target/ppc/kvm.c | 18 -----
> > target/ppc/kvm_ppc.h | 6 --
> > 8 files changed, 184 insertions(+), 24 deletions(-)
> > create mode 100644 docs/papr-pef.txt
> > create mode 100644 hw/ppc/pef.c
> > create mode 100644 include/hw/ppc/pef.h
> >
> > diff --git a/docs/confidential-guest-support.txt b/docs/confidential-guest-support.txt
> > index 2790425b38..f0801814ff 100644
> > --- a/docs/confidential-guest-support.txt
> > +++ b/docs/confidential-guest-support.txt
> > @@ -40,4 +40,7 @@ Currently supported confidential guest mechanisms are:
> > AMD Secure Encrypted Virtualization (SEV)
> > docs/amd-memory-encryption.txt
> >
> > +POWER Protected Execution Facility (PEF)
> > + docs/papr-pef.txt
> > +
> > Other mechanisms may be supported in future.
> > diff --git a/docs/papr-pef.txt b/docs/papr-pef.txt
> > new file mode 100644
> > index 0000000000..6419e995cf
> > --- /dev/null
> > +++ b/docs/papr-pef.txt
>
> Same here, make this .rst and add it to the system guide?

Again, I feel like I'm sufficiently bogged down in bikeshedding the
technical details to feel inclined to block it on a nice-to-have like
this.

> > @@ -0,0 +1,30 @@
> > +POWER (PAPR) Protected Execution Facility (PEF)
> > +===============================================
> > +
> > +Protected Execution Facility (PEF), also known as Secure Guest support
> > +is a feature found on IBM POWER9 and POWER10 processors.
> > +
> > +If a suitable firmware including an Ultravisor is installed, it adds
> > +an extra memory protection mode to the CPU. The ultravisor manages a
> > +pool of secure memory which cannot be accessed by the hypervisor.
> > +
> > +When this feature is enabled in qemu, a guest can use ultracalls to
>
> s/qemu/QEMU/

Fixed.

> > +enter "secure mode". This transfers most of its memory to secure
> > +memory, where it cannot be eavesdropped by a compromised hypervisor.
> > +
> > +Launching
> > +---------
> > +
> > +To launch a guest which will be permitted to enter PEF secure mode:
> > +
> > +# ${QEMU} \
> > + -object pef-guest,id=pef0 \
> > + -machine confidential-guest-support=pef0 \
> > + ...
> > +
> > +Live Migration
> > +----------------
> > +
> > +Live migration is not yet implemented for PEF guests. For
> > +consistency, we currently prevent migration if the PEF feature is
> > +enabled, whether or not the guest has actually entered secure mode.
> > diff --git a/hw/ppc/meson.build b/hw/ppc/meson.build
> > index ffa2ec37fa..218631c883 100644
> > --- a/hw/ppc/meson.build
> > +++ b/hw/ppc/meson.build
> > @@ -27,6 +27,7 @@ ppc_ss.add(when: 'CONFIG_PSERIES', if_true: files(
> > 'spapr_nvdimm.c',
> > 'spapr_rtas_ddw.c',
> > 'spapr_numa.c',
> > + 'pef.c',
> > ))
> > ppc_ss.add(when: 'CONFIG_SPAPR_RNG', if_true: files('spapr_rng.c'))
> > ppc_ss.add(when: ['CONFIG_PSERIES', 'CONFIG_LINUX'], if_true: files(
> > diff --git a/hw/ppc/pef.c b/hw/ppc/pef.c
> > new file mode 100644
> > index 0000000000..02b9b3b460
> > --- /dev/null
> > +++ b/hw/ppc/pef.c
> > @@ -0,0 +1,119 @@
> > +/*
> > + * PEF (Protected Execution Facility) for POWER support
> > + *
> > + * Copyright David Gibson, Redhat Inc. 2020
>
> 2021?

So, it happens that in the meantime I've had different cause to look
up what Red Hat actually recommends as the copyright notice in open
source files, and it turns out they suggest simply "Copyright Red
Hat", with no names or dates. So I'll switch to that for all the new
files in the series.

> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> > + * See the COPYING file in the top-level directory.
> > + *
> > + */
> > +
>

--
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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