Re: [PATCH v6 10/13] spapr: Add PEF based confidential guest support

[Daniel P . Berrangé]

On Tue, Jan 12, 2021 at 03:45:05PM +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 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 |   2 +
>  docs/papr-pef.txt                   |  30 ++++++++
>  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 --
>  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/hw/ppc/pef.c b/hw/ppc/pef.c
> new file mode 100644
> index 0000000000..b227dc6905
> --- /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/confidential-guest-support.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;

Can use  OBJECT_DECLARE_TYPE.

Also the struct naming ought to match the type naming.
eg use PefGuest for the struct, to match TYPE_PEF_GUEST.

> +
> +/**
> + * PefGuestState:
> + *
> + * The PefGuestState object is used for creating and managing a PEF
> + * guest.
> + *
> + * # $QEMU \
> + *         -object pef-guest,id=pef0 \
> + *         -machine ...,confidential-guest-support=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_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;
> +}
> +
> +/*
> + * Don't set error if KVM_PPC_SVM_OFF ioctl is invoked on kernels
> + * that don't support this ioctl.
> + */
> +void kvmppc_svm_off(Error **errp)
> +{
> +    int rc;
> +
> +    if (!kvm_enabled()) {
> +        return;
> +    }
> +
> +    rc = kvm_vm_ioctl(KVM_STATE(current_accel()), KVM_PPC_SVM_OFF);
> +    if (rc && rc != -ENOTTY) {
> +        error_setg_errno(errp, -rc, "KVM_PPC_SVM_OFF ioctl failed");
> +    }
> +}
> +#else
> +static int kvmppc_svm_init(Error **errp)
> +{
> +    g_assert_not_reached();
> +}
> +#endif
> +
> +int pef_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
> +{
> +    if (!object_dynamic_cast(OBJECT(cgs), TYPE_PEF_GUEST)) {
> +        return 0;
> +    }
> +
> +    if (!kvm_enabled()) {
> +        error_setg(errp, "PEF requires KVM");
> +        return -1;
> +    }
> +
> +    return kvmppc_svm_init(errp);
> +}
> +
> +static const TypeInfo pef_guest_info = {
> +    .parent = TYPE_OBJECT,
> +    .name = TYPE_PEF_GUEST,
> +    .instance_size = sizeof(PefGuestState),
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_CONFIDENTIAL_GUEST_SUPPORT },
> +        { TYPE_USER_CREATABLE },
> +        { }
> +    }
> +};
> +
> +static void
> +pef_register_types(void)
> +{
> +    type_register_static(&pef_guest_info);
> +}
> +
> +type_init(pef_register_types);

Can use OBJECT_DEFINE_TYPE_WITH_INTERFACES here


Regards,
Daniel
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