Re: [PATCH v2 00/21] hw/uefi: add uefi variable service

[Daniel P . Berrangé]

On Wed, Jan 08, 2025 at 03:53:21PM +0400, Marc-André Lureau wrote:
> Hi
> 
> On Tue, Jan 7, 2025 at 7:34 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
> >
> > This patch adds a virtual device to qemu which the uefi firmware can use
> > to store variables.  This moves the UEFI variable management from
> > privileged guest code (managing vars in pflash) to the host.  Main
> > advantage is that the need to have privilege separation in the guest
> > goes away.
> >
> > On x86 privileged guest code runs in SMM.  It's supported by kvm, but
> > not liked much by various stakeholders in cloud space due to the
> > complexity SMM emulation brings.
> >
> > On arm privileged guest code runs in el3 (aka secure world).  This is
> > not supported by kvm, which is unlikely to change anytime soon given
> > that even el2 support (nested virt) is being worked on for years and is
> > not yet in mainline.
> >
> > The design idea is to reuse the request serialization protocol edk2 uses
> 
> I suppose this is a stable protocol. (some parts are set by the UEFI
> spec probably)
> 
> There doesn't seem to be a defined way to query either side version or
> capability, I suppose this could be added later assuming an initial
> behaviour/magic etc.
> 
> > for communication between SMM and non-SMM code, so large chunks of the
> > edk2 variable driver stack can be used unmodified.  Only the driver
> > which traps into SMM mode must be replaced by a driver which talks to
> > qemu instead.
> >
> > A edk2 test branch can be found here (build with "-D QEMU_VARS=TRUE").
> > https://github.com/kraxel/edk2/commits/devel/secure-boot-external-vars
> >
> 
> ok, perhaps it would be nice to have some basic unit tests in qemu
> too. Almost none of this new code is exercised by the qemu tests yet.
> 
> > The uefi-vars device re-implements the privileged edk2 protocols
> > (i.e. the code running in SMM mode).
> 
> Typically the kind of new code that I wish would be in Rust. But I
> suppose it is too early yet, and you came to the same conclusion.
> Probably a good candidate for rewrite though!

Perhaps too early for the device impl, but I would have thought
the general var-service code could be done in rust today. It does
not have all that much interaction with other parts of the QEMU
codebase & thus wouldn't be building on the moving target of the
QOM/Device abstractions. It would also be the prime part that
could be shared with coconut-svsm too.

> 
> >
> > v2 changes:
> >  - fully implement authenticated variables.
> >  - various cleanups and fixes.
> >
> > enjoy & take care,
> >   Gerd
> >
> > Gerd Hoffmann (21):
> >   hw/uefi: add include/hw/uefi/var-service-api.h
> >   hw/uefi: add include/hw/uefi/var-service-edk2.h
> >   hw/uefi: add include/hw/uefi/var-service.h
> >   hw/uefi: add var-service-guid.c
> >   hw/uefi: add var-service-utils.c
> >   hw/uefi: add var-service-vars.c
> >   hw/uefi: add var-service-auth.c
> >   hw/uefi: add var-service-policy.c
> >   hw/uefi: add var-service-core.c
> >   hw/uefi: add var-service-pkcs7.c
> >   hw/uefi: add var-service-pkcs7-stub.c
> >   hw/uefi: add var-service-siglist.c
> >   hw/uefi: add var-service-json.c + qapi for NV vars.
> >   hw/uefi: add trace-events
> >   hw/uefi: add UEFI_VARS to Kconfig
> >   hw/uefi: add to meson
> >   hw/uefi: add uefi-vars-sysbus device
> >   hw/uefi: add uefi-vars-isa device
> >   hw/arm: add uefi variable support to virt machine type
> >   docs: add uefi variable service documentation
> >   hw/uefi: add MAINTAINERS entry
> >
> >  include/hw/arm/virt.h              |   2 +
> >  include/hw/uefi/var-service-api.h  |  40 ++
> >  include/hw/uefi/var-service-edk2.h | 227 +++++++++
> >  include/hw/uefi/var-service.h      | 186 ++++++++
> >  hw/arm/virt.c                      |  41 ++
> >  hw/uefi/var-service-auth.c         | 361 ++++++++++++++
> >  hw/uefi/var-service-core.c         | 237 ++++++++++
> >  hw/uefi/var-service-guid.c         |  99 ++++
> >  hw/uefi/var-service-isa.c          |  91 ++++
> >  hw/uefi/var-service-json.c         | 242 ++++++++++
> >  hw/uefi/var-service-pkcs7-stub.c   |  16 +
> >  hw/uefi/var-service-pkcs7.c        | 436 +++++++++++++++++
> >  hw/uefi/var-service-policy.c       | 370 +++++++++++++++
> >  hw/uefi/var-service-siglist.c      | 212 +++++++++
> >  hw/uefi/var-service-sysbus.c       |  90 ++++
> >  hw/uefi/var-service-utils.c        | 241 ++++++++++
> >  hw/uefi/var-service-vars.c         | 725 +++++++++++++++++++++++++++++
> >  MAINTAINERS                        |   6 +
> >  docs/devel/index-internals.rst     |   1 +
> >  docs/devel/uefi-vars.rst           |  66 +++
> >  hw/Kconfig                         |   1 +
> >  hw/meson.build                     |   1 +
> >  hw/uefi/Kconfig                    |   9 +
> >  hw/uefi/LIMITATIONS.md             |   7 +
> >  hw/uefi/meson.build                |  24 +
> >  hw/uefi/trace-events               |  17 +
> >  meson.build                        |   1 +
> >  qapi/meson.build                   |   1 +
> >  qapi/qapi-schema.json              |   1 +
> >  qapi/uefi.json                     |  45 ++
> >  30 files changed, 3796 insertions(+)
> >  create mode 100644 include/hw/uefi/var-service-api.h
> >  create mode 100644 include/hw/uefi/var-service-edk2.h
> >  create mode 100644 include/hw/uefi/var-service.h
> >  create mode 100644 hw/uefi/var-service-auth.c
> >  create mode 100644 hw/uefi/var-service-core.c
> >  create mode 100644 hw/uefi/var-service-guid.c
> >  create mode 100644 hw/uefi/var-service-isa.c
> >  create mode 100644 hw/uefi/var-service-json.c
> >  create mode 100644 hw/uefi/var-service-pkcs7-stub.c
> >  create mode 100644 hw/uefi/var-service-pkcs7.c
> >  create mode 100644 hw/uefi/var-service-policy.c
> >  create mode 100644 hw/uefi/var-service-siglist.c
> >  create mode 100644 hw/uefi/var-service-sysbus.c
> >  create mode 100644 hw/uefi/var-service-utils.c
> >  create mode 100644 hw/uefi/var-service-vars.c
> >  create mode 100644 docs/devel/uefi-vars.rst
> >  create mode 100644 hw/uefi/Kconfig
> >  create mode 100644 hw/uefi/LIMITATIONS.md
> >  create mode 100644 hw/uefi/meson.build
> >  create mode 100644 hw/uefi/trace-events
> >  create mode 100644 qapi/uefi.json
> >
> > --
> > 2.47.1
> >
> 

With regards,
Daniel
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