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

[Dr. David Alan Gilbert]

* David Gibson (david@gibson.dropbear.id.au) wrote:
> On Mon, Jan 18, 2021 at 06:51:24PM +0000, Dr. David Alan Gilbert wrote:
> > * David Gibson (david@gibson.dropbear.id.au) 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
> >                                                            ^^^^^
> > (and below) My understanding is that it's Intel TDX that's the VM
> > equivalent.
> 
> I thought MKTME could already do memory encryption and TDX extended
> that to... more?  I'll adjust the comment to say TDX anyway, since
> that seems to be the newer name.

My understanding was MKTME does the memory encryption, but doesn't
explicitly wire that into VMs or attestation of VMs or anything like
that.  TDX wires that encryption to VMs and provides all the other glue
that goes with attestation and the like.

Dave

> > 
> > Dave
> > 
> > > 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,
> > >      .name = TYPE_SEV_GUEST,
> > >      .instance_size = sizeof(SevGuestState),
> > >      .instance_finalize = sev_guest_finalize,
> 
> -- 
> 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


-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK