[PATCH v1 1/2] EDK2 Code First: PI Specification: New error codes of Host Software class

["Kun Qin" <kuqin12@gmail.com>]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3794

This change includes specification update markdown file that describes
the proposed PI Specification v1.7 Errata A in detail and potential
impact to the existing codebase.

Cc: Andrew Fish <afish@apple.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>

Signed-off-by: Kun Qin <kuqin12@gmail.com>
---
 CodeFirst/BZ3794-SpecChange.md | 60 ++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/CodeFirst/BZ3794-SpecChange.md b/CodeFirst/BZ3794-SpecChange.md
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+# Title: Introduction of `EFI_MM_COMMUNICATE_HEADER_V3` and `MM_COMMUNICATE3_*` interface
+
+## Status: Draft
+
+## Document: UEFI Platform Initialization Specification Version 1.7 Errata A
+
+## License
+
+SPDX-License-Identifier: CC-BY-4.0
+
+## Submitter: [TianoCore Community](https://www.tianocore.org)
+
+## Summary of the change
+
+Introduce `EFI_SW_EC_MEMORY_TYPE_INFORMATION_CHANGE` and `EFI_SW_EC_RELEASE_ASSERT` into Status Codes definition.
+
+## Benefits of the change
+
+Current Status Codes covered various [software class error code definitions](https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Pi/PiStatusCode.h).
+
+However, there are a few critical instances where the software could trigger system reboots while the corresponding case was not covered by the already defined status codes:
+
+1. Memory type information change triggered system reboot;
+2. Assert triggered reboot on systems that did not enable system halts;
+
+The unexpected system reboots above could indicate decay of system health and reporting of such generic events would provide helpful information to OEMs to investigate/prevent system failures in general.
+
+The request of this change intends to expand definitions of `EFI_SW_EC_**` under Status Codes to cover more unexpected system reboot events, which could improve Status Code futility and readability.
+
+## Impact of the change
+
+Occupy 2 new macro definitions of Error Codes under Software class Status Codes.
+
+## Detailed description of the change [normative updates]
+
+### Specification Changes
+
+1. In PI Specification v1.7 Errata A: Vol. 3, Table 3-61: Error Code Operations: Host Software Class, add 2 new rows below `EFI_SW_EC_FV_CORRUPTED` definition:
+
+    | Operation | Description | Extended Data |
+    | --- | --- | --- |
+    | EFI_SW_EC_MEMORY_TYPE_INFORMATION_CHANGE | System will reboot due to memory type information changes | None |
+    | EFI_SW_EC_RELEASE_ASSERT | System software asserted  | None |
+
+1. In PI Specification v1.7 Errata A: Vol. 3, Table 3-61: Error Code Operations: Host Software Class, replace the row of `0x0014–0x00FF` to:
+
+    | Operation | Description | Extended Data |
+    | --- | --- | --- |
+    | 0x0016–0x00FF | Reserved for future use by this specification for Host Software class error codes. | None |
+
+1. In PI Specification v1.7 Errata A: Vol. 3, Section 6.7.4.3 Error Code Definitions: Prototype, add 2 new definitions below `EFI_SW_EC_FV_CORRUPTED` definition:
+
+    ```c
+    #define EFI_SW_EC_MEMORY_TYPE_INFORMATION_CHANGE  0x00000014
+    #define EFI_SW_EC_RELEASE_ASSERT                  0x00000015
+    ```
+
+### Code Changes
+
+1. Add macro definitions in `MdePkg/Include/Pi/PiStatusCode.h` to match new specification.
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