Re: [PATCH v7 02/13] confidential guest support: Introduce new confidential guest support class

David Gibson
2021-01-14T11:47:10Z

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On Thu, Jan 14, 2021 at 09:34:36AM +0000, Daniel P. Berrangé wrote:
> On Thu, Jan 14, 2021 at 10:58:00AM +1100, David Gibson wrote:
> > Several architectures have mechanisms which are designed to protect guest
> > memory from interference or eavesdropping by a compromised hypervisor. AMD
> > SEV does this with in-chip memory encryption and Intel's MKTME can do
> > similar things. POWER's Protected Execution Framework (PEF) accomplishes a
> > similar goal using an ultravisor and new memory protection features,
> > instead of encryption.
> >
> > To (partially) unify handling for these, this introduces a new
> > ConfidentialGuestSupport QOM base class. "Confidential" is kind of vague,
> > but "confidential computing" seems to be the buzzword about these schemes,
> > and "secure" or "protected" are often used in connection to unrelated
> > things (such as hypervisor-from-guest or guest-from-guest security).
> >
> > The "support" in the name is significant because in at least some of the
> > cases it requires the guest to take specific actions in order to protect
> > itself from hypervisor eavesdropping.
> >
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> > backends/confidential-guest-support.c | 33 ++++++++++++++++++++
> > backends/meson.build | 1 +
> > include/exec/confidential-guest-support.h | 38 +++++++++++++++++++++++
> > include/qemu/typedefs.h | 1 +
> > target/i386/sev.c | 3 +-
> > 5 files changed, 75 insertions(+), 1 deletion(-)
> > create mode 100644 backends/confidential-guest-support.c
> > create mode 100644 include/exec/confidential-guest-support.h
> >
> > diff --git a/backends/confidential-guest-support.c b/backends/confidential-guest-support.c
> > new file mode 100644
> > index 0000000000..9b0ded0db4
> > --- /dev/null
> > +++ b/backends/confidential-guest-support.c
> > @@ -0,0 +1,33 @@
> > +/*
> > + * QEMU Confidential Guest support
> > + *
> > + * Copyright: David Gibson, Red Hat Inc. 2020
> > + *
> > + * Authors:
> > + * David Gibson <david@gibson.dropbear.id.au>
> > + *
> > + * 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 "exec/confidential-guest-support.h"
> > +
> > +OBJECT_DEFINE_ABSTRACT_TYPE(ConfidentialGuestSupport,
> > + confidential_guest_support,
> > + CONFIDENTIAL_GUEST_SUPPORT,
> > + OBJECT)
> > +
> > +static void confidential_guest_support_class_init(ObjectClass *oc, void *data)
> > +{
> > +}
> > +
> > +static void confidential_guest_support_init(Object *obj)
> > +{
> > +}
> > +
> > +static void confidential_guest_support_finalize(Object *obj)
> > +{
> > +}
> > diff --git a/backends/meson.build b/backends/meson.build
> > index 484456ece7..d4221831fc 100644
> > --- a/backends/meson.build
> > +++ b/backends/meson.build
> > @@ -6,6 +6,7 @@ softmmu_ss.add([files(
> > 'rng-builtin.c',
> > 'rng-egd.c',
> > 'rng.c',
> > + 'confidential-guest-support.c',
> > ), numa])
> >
> > softmmu_ss.add(when: 'CONFIG_POSIX', if_true: files('rng-random.c'))
> > diff --git a/include/exec/confidential-guest-support.h b/include/exec/confidential-guest-support.h
> > new file mode 100644
> > index 0000000000..5f131023ba
> > --- /dev/null
> > +++ b/include/exec/confidential-guest-support.h
> > @@ -0,0 +1,38 @@
> > +/*
> > + * QEMU Confidential Guest support
> > + * This interface describes the common pieces between various
> > + * schemes for protecting guest memory or other state against a
> > + * compromised hypervisor. This includes memory encryption (AMD's
> > + * SEV and Intel's MKTME) or special protection modes (PEF on POWER,
> > + * or PV on s390x).
> > + *
> > + * Copyright: David Gibson, Red Hat Inc. 2020
> > + *
> > + * Authors:
> > + * David Gibson <david@gibson.dropbear.id.au>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or
> > + * later. See the COPYING file in the top-level directory.
> > + *
> > + */
> > +#ifndef QEMU_CONFIDENTIAL_GUEST_SUPPORT_H
> > +#define QEMU_CONFIDENTIAL_GUEST_SUPPORT_H
> > +
> > +#ifndef CONFIG_USER_ONLY
> > +
> > +#include "qom/object.h"
> > +
> > +#define TYPE_CONFIDENTIAL_GUEST_SUPPORT "confidential-guest-support"
> > +OBJECT_DECLARE_SIMPLE_TYPE(ConfidentialGuestSupport, CONFIDENTIAL_GUEST_SUPPORT)
> > +
> > +struct ConfidentialGuestSupport {
> > + Object parent;
> > +};
> > +
> > +typedef struct ConfidentialGuestSupportClass {
> > + ObjectClass parent;
> > +} ConfidentialGuestSupportClass;
> > +
> > +#endif /* !CONFIG_USER_ONLY */
> > +
> > +#endif /* QEMU_CONFIDENTIAL_GUEST_SUPPORT_H */
> > diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
> > index 976b529dfb..33685c79ed 100644
> > --- a/include/qemu/typedefs.h
> > +++ b/include/qemu/typedefs.h
> > @@ -36,6 +36,7 @@ typedef struct BusState BusState;
> > typedef struct Chardev Chardev;
> > typedef struct CompatProperty CompatProperty;
> > typedef struct CoMutex CoMutex;
> > +typedef struct ConfidentialGuestSupport ConfidentialGuestSupport;
> > typedef struct CPUAddressSpace CPUAddressSpace;
> > typedef struct CPUState CPUState;
> > typedef struct DeviceListener DeviceListener;
> > diff --git a/target/i386/sev.c b/target/i386/sev.c
> > index 1546606811..6b49925f51 100644
> > --- a/target/i386/sev.c
> > +++ b/target/i386/sev.c
> > @@ -31,6 +31,7 @@
> > #include "qom/object.h"
> > #include "exec/address-spaces.h"
> > #include "monitor/monitor.h"
> > +#include "exec/confidential-guest-support.h"
> >
> > #define TYPE_SEV_GUEST "sev-guest"
> > OBJECT_DECLARE_SIMPLE_TYPE(SevGuestState, SEV_GUEST)
> > @@ -322,7 +323,7 @@ sev_guest_instance_init(Object *obj)
> >
> > /* sev guest info */
> > static const TypeInfo sev_guest_info = {
> > - .parent = TYPE_OBJECT,
> > + .parent = TYPE_CONFIDENTIAL_GUEST_SUPPORT,
>
> If you're changing the parent QOM type, then you also need to change
> the parent struct field type in SevguestState to match

Oops, yes. I checked the rest of the types as I made the
OBJECT_DECLARE_TYPE conversions, but I forgot to go back and check
SEV.

> > .name = TYPE_SEV_GUEST,
> > .instance_size = sizeof(SevGuestState),
> > .instance_finalize = sev_guest_finalize,
>
> Regards,
> Daniel

--
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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