[PATCH 0/4] MdeModulePkg, StandaloneMmPkg: work around VA vs PA ambiguity

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

This series proposes one possible approach to work around the issue that the
traditional MM and standalone MM implement versions of the communicate protocol
that are fundamentally incompatible from the point of view of the caller.

In traditional MM, the MM communicate protocol takes a physical pointer for
the buffer, so that the SMM execution context can access the memory directly
without having to translate it according to the translation regime of the
caller.

In standalone MM, the buffer that is shared with the MM context is preallocated,
and so it is up to the implementation of the MM communicate protocol to copy the
data from the caller allocated buffer into the preallocated shared buffer. In
order to be able to do so, the DXE driver needs to copy the contents, and for
this it needs to know the virtual address not the physical address.

So this means we have two incompatible versions of the same protocol, and given
that we have even re-used the EFI_SMM_COMMUNICATE_PROTOCOL GUID for the new
EFI_MM_COMMUNICATE_PROTOCOL, we cannot distinguish programmatically between a
MM context that takes physical addresses vs one that takes virtual ones.

Since this is known at build time, one way to deal with this is to have two
different implementations of a library that defines an abstract MmCommunicate()
function, allowing the correct implementation to be selected at integration
time.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Achin Gupta <achin.gupta@arm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Supreeth Venkatesh <supreeth.venkatesh@arm.com>
Cc: Jagadeesh Ujja <jagadeesh.ujja@arm.com>

Ard Biesheuvel (4):
  MdeModulePkg: introduce MmCommunicationLib library class
  MdeModulePkg: add implementation of MmCommunicateLib
  StandaloneMmPkg: add implementation of MmCommunicateLib
  MdeModulePkg/VariableSmmRuntimeDxe: switch to MmCommunicateLib library

 MdeModulePkg/MdeModulePkg.dec                                                     |   4 +
 MdeModulePkg/MdeModulePkg.dsc                                                     |   2 +
 MdeModulePkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.inf    |  51 +++++++++
 MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.inf              |   4 +-
 StandaloneMmPkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.inf |  51 +++++++++
 MdeModulePkg/Include/Library/MmCommunicateLib.h                                   |  50 +++++++++
 MdeModulePkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.c      | 114 ++++++++++++++++++++
 MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.c                |  10 +-
 StandaloneMmPkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.c   | 113 +++++++++++++++++++
 MdeModulePkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.uni    |  19 ++++
 StandaloneMmPkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.uni |  19 ++++
 11 files changed, 428 insertions(+), 9 deletions(-)
 create mode 100644 MdeModulePkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.inf
 create mode 100644 StandaloneMmPkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.inf
 create mode 100644 MdeModulePkg/Include/Library/MmCommunicateLib.h
 create mode 100644 MdeModulePkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.c
 create mode 100644 StandaloneMmPkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.c
 create mode 100644 MdeModulePkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.uni
 create mode 100644 StandaloneMmPkg/Library/RuntimeDxeMmCommunicateLib/RuntimeDxeMmCommunicateLib.uni

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2.20.1