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

[Ram Pai]

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.

RP