Re: [for-6.0 v5 10/13] spapr: Add PEF based securable guest memory

[David Gibson]

On Tue, Jan 05, 2021 at 03:34:38PM -0800, Ram Pai wrote:
> On Fri, Dec 04, 2020 at 04:44:12PM +1100, David Gibson 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 securable-guest-memory machine
> > 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 securable-guest-memory=pef0
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > Acked-by: Ram Pai <linuxram@us.ibm.com>
> > ---
> >  hw/ppc/meson.build   |   1 +
> >  hw/ppc/pef.c         | 115 +++++++++++++++++++++++++++++++++++++++++++
> >  hw/ppc/spapr.c       |  10 ++++
> >  include/hw/ppc/pef.h |  26 ++++++++++
> >  target/ppc/kvm.c     |  18 -------
> >  target/ppc/kvm_ppc.h |   6 ---
> >  6 files changed, 152 insertions(+), 24 deletions(-)
> >  create mode 100644 hw/ppc/pef.c
> >  create mode 100644 include/hw/ppc/pef.h
> > 
> > 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..3ae3059cfe
> > --- /dev/null
> > +++ b/hw/ppc/pef.c
> > @@ -0,0 +1,115 @@
> > +/*
> > + * PEF (Protected Execution Facility) for POWER support
> > + *
> > + * Copyright David Gibson, Redhat Inc. 2020
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or 
> > later.
> > + * See the COPYING file in the top-level directory.
> > + *
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +
> > +#include "qapi/error.h"
> > +#include "qom/object_interfaces.h"
> > +#include "sysemu/kvm.h"
> > +#include "migration/blocker.h"
> > +#include "exec/securable-guest-memory.h"
> > +#include "hw/ppc/pef.h"
> > +
> > +#define TYPE_PEF_GUEST "pef-guest"
> > +#define PEF_GUEST(obj)                                  \
> > +    OBJECT_CHECK(PefGuestState, (obj), TYPE_PEF_GUEST)
> > +
> > +typedef struct PefGuestState PefGuestState;
> > +
> > +/**
> > + * PefGuestState:
> > + *
> > + * The PefGuestState object is used for creating and managing a PEF
> > + * guest.
> > + *
> > + * # $QEMU \
> > + *         -object pef-guest,id=pef0 \
> > + *         -machine ...,securable-guest-memory=pef0
> > + */
> > +struct PefGuestState {
> > +    Object parent_obj;
> > +};
> > +
> > +#ifdef CONFIG_KVM
> > +static int kvmppc_svm_init(Error **errp)
> > +{
> > +    if (!kvm_check_extension(kvm_state, KVM_CAP_PPC_SECURABLE_GUEST)) {
>                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^
> KVM defines this macro as KVM_CAP_PPC_SECURE_GUEST. Unless we patch KVM,
>     we are stuck with KVM_CAP_PPC_SECURE_GUEST.

Oops, made an over-zealous search and replace.  Fixed now.

-- 
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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