PrmPkg: Add ALLOCATE_CONTEXT_BUFFER_IN_FW build option

There's currently two approaches being considered for how to allocate the
context buffer passed to PRM handlers:

1. The context buffer is allocated and populated in firmware. As such, the
   FW converts all pointers internal to the buffer to virtual memory
   addresses at the virtual address change event. A single context buffer
   pointer is given to the OS via the PRM ACPI table and the OS converts
   this single physical address to a virtual address when it passes the
   context buffer as a pointer to PRM handlers.

2. The context buffer is allocated and populated in the OS. The OS gets
   all the information needed to populate the context buffer from other
   pre-existing resources (mainly physical addresses in the PRM ACPI
   table). The OS converts all the physical addresses to virtual addresses,
   allocates the context buffer instances, and fills in the information.
   The OS passes the context buffer virtual address to PRM handlers.

The prior behavior was (1). The current POR behavior has moved to (2).
Until (2) is used more widely, it can be kept around with fairly minimal
overhead via a build flag in a few places.

So the default behavior is now (2) (the expected permanent behavior) with
(1) easily enabled by defining "ALLOCATE_CONTEXT_BUFFER_IN_FW" in the
compiler defined macros. A DSC define was added in PrmPkg.dsc to set this
compiler macro in the package  build.

At some point in the future, all code (and some peripheral code)
surrounded with this build flag can be removed if (2) is fully
decided upon.

Cc: Andrew Fish <afish@apple.com>
Cc: Kang Gao <kang.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Benjamin You <benjamin.you@intel.com>
Cc: Liu Yun <yun.y.liu@intel.com>
Cc: Ankit Sinha <ankit.sinha@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Acked-by: Michael D Kinney <michael.d.kinney@intel.com>
Acked-by: Liming Gao <gaoliming@byosoft.com.cn>
Acked-by: Leif Lindholm <quic_llindhol@quicinc.com>
Reviewed-by: Ankit Sinha <ankit.sinha@intel.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/PrmPkg/Samples/PrmSampleContextBufferModule/Library/DxeContextBufferModuleConfigLib/DxeContextBufferModuleConfigLib.c b/PrmPkg/Samples/PrmSampleContextBufferModule/Library/DxeContextBufferModuleConfigLib/DxeContextBufferModuleConfigLib.c
index 3bf5beba7d..b0b12c012a 100644
--- a/PrmPkg/Samples/PrmSampleContextBufferModule/Library/DxeContextBufferModuleConfigLib/DxeContextBufferModuleConfigLib.c
+++ b/PrmPkg/Samples/PrmSampleContextBufferModule/Library/DxeContextBufferModuleConfigLib/DxeContextBufferModuleConfigLib.c
@@ -151,10 +151,26 @@ ContextBufferModuleConfigLibConstructor (
   //

   // Allocate and populate the context buffer

   //

+#ifdef ALLOCATE_CONTEXT_BUFFER_IN_FW

+  //

+  // The context buffer allocated in FW will continue being used at OS runtime so it must

+  // be a runtime services data buffer.

+  //

   // This sample module uses a single context buffer for all the handlers

   // Todo: This can be done more elegantly in the future. Likely though a library service.

   //

   PrmContextBuffer = AllocateRuntimeZeroPool (sizeof (*PrmContextBuffer));

+#else

+  //

+  // This context buffer is not actually used by PRM handler at OS runtime. The OS will allocate

+  // the actual context buffer passed to the PRM handler.

+  //

+  // This context buffer is used internally in the firmware to associate a PRM handler with a

+  // a static data buffer and a runtime MMIO ranges array so those can be placed into the

+  // PRM_HANDLER_INFORMATION_STRUCT and PRM_MODULE_INFORMATION_STRUCT respectively for the PRM handler.

+  //

+  PrmContextBuffer = AllocateZeroPool (sizeof (*PrmContextBuffer));

+#endif

   ASSERT (PrmContextBuffer != NULL);

   if (PrmContextBuffer == NULL) {

     Status = EFI_OUT_OF_RESOURCES;