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

[Cornelia Huck]

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?

> @@ -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/

> +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?

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