Re: [RFC v2 17/18] spapr: Added PEF based guest memory protection

[Greg Kurz <groug@kaod.org>]

On Thu, 21 May 2020 13:43:03 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> Some upcoming POWER machines have a system called PEF (Protected
> Execution Framework) which uses a small ultravisor to allow guests to

s/Framework/Facility

> 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 havint the right hardware and firmware, we don't

s/havint/having

> enable this by default.  In order to run a secure guest you need to
> create a "pef-guest" object and set the guest-memory-protection machine property to point to it.
> 

Wrap line after "machine" maybe ?

> 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, so we can't know if the guest actually is secure until
> well after machine creation time.
> 

Maybe worth mentioning that this is for KVM only. Also, this is
silently ignored with TCG since pef_kvm_init() isn't called in
this case. Would it make sense to print some warning like we
do for these spapr caps that we don't support with TCG ?

> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  target/ppc/Makefile.objs |  2 +-
>  target/ppc/pef.c         | 81 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 82 insertions(+), 1 deletion(-)
>  create mode 100644 target/ppc/pef.c
> 
> diff --git a/target/ppc/Makefile.objs b/target/ppc/Makefile.objs
> index e8fa18ce13..ac93b9700e 100644
> --- a/target/ppc/Makefile.objs
> +++ b/target/ppc/Makefile.objs
> @@ -6,7 +6,7 @@ obj-y += machine.o mmu_helper.o mmu-hash32.o monitor.o arch_dump.o
>  obj-$(TARGET_PPC64) += mmu-hash64.o mmu-book3s-v3.o compat.o
>  obj-$(TARGET_PPC64) += mmu-radix64.o
>  endif
> -obj-$(CONFIG_KVM) += kvm.o
> +obj-$(CONFIG_KVM) += kvm.o pef.o
>  obj-$(call lnot,$(CONFIG_KVM)) += kvm-stub.o
>  obj-y += dfp_helper.o
>  obj-y += excp_helper.o
> diff --git a/target/ppc/pef.c b/target/ppc/pef.c
> new file mode 100644
> index 0000000000..823daf3e9c
> --- /dev/null
> +++ b/target/ppc/pef.c
> @@ -0,0 +1,81 @@
> +/*
> + * PEF (Protected Execution Framework) for POWER support

s/Framework/Facility

> + *
> + * 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"
> +

I had to include some more headers to build this.

#include "exec/guest-memory-protection.h"
#include "qapi/error.h"
#include "qom/object_interfaces.h"
#include "sysemu/kvm.h"

> +#define TYPE_PEF_GUEST "pef-guest"
> +#define PEF_GUEST(obj)                                  \
> +    OBJECT_CHECK(PefGuestState, (obj), TYPE_SEV_GUEST)

s/TYPE_SEV_GUEST/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 ...,guest-memory-protection=pef0
> + */
> +struct PefGuestState {
> +    Object parent_obj;
> +};
> +
> +static Error *pef_mig_blocker;

Unused.

> +
> +static int pef_kvm_init(GuestMemoryProtection *gmpo, Error **errp)
> +{
> +    PefGuestState *pef = PEF_GUEST(gmpo);

Unused.

> +
> +    if (!kvm_check_extension(kvm_state, KVM_CAP_PPC_SECURE_GUEST)) {
> +        error_setg(errp,
> +                   "KVM implementation does not support Secure VMs (is an ultravisor running?)");
> +        return -1;
> +    } else {
> +        int ret = kvm_vm_enable_cap(kvm_state, KVM_CAP_PPC_SECURE_GUEST, 0, 1);
> +
> +        if (ret < 0) {
> +            error_setg(errp,
> +                       "Error enabling PEF with KVM");
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static void pef_guest_class_init(ObjectClass *oc, void *data)
> +{
> +    GuestMemoryProtectionClass *gmpc = GUEST_MEMORY_PROTECTION_CLASS(oc);
> +
> +    gmpc->kvm_init = pef_kvm_init;
> +}
> +
> +static const TypeInfo pef_guest_info = {
> +    .parent = TYPE_OBJECT,
> +    .name = TYPE_PEF_GUEST,
> +    .instance_size = sizeof(PefGuestState),
> +    .class_init = pef_guest_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_GUEST_MEMORY_PROTECTION },
> +        { TYPE_USER_CREATABLE },
> +        { }
> +    }
> +};
> +
> +static void
> +pef_register_types(void)
> +{
> +    type_register_static(&pef_guest_info);
> +}
> +
> +type_init(pef_register_types);