This changeset introduces support for the ACPI Error Record
Serialization Table, ERST.
ERST is defined in [1], and the error records are defined
according to [2].
This changeset generates the ACPI ERST table, which OSPM
follows to program the associated ERST device. The ERST
device occupies 8KiB of address space, with the first 8 bytes
containing registers, and the remainder being an exchange
buffer for reading/writing error records.
The ERST device contains two registers, ACTION and VALUE
registers, following closely the ERST operations.
The ERST device only examines the record for the signature 'CPER',
its record identifier, and bounds-checks the length against the size
of the the CPER record header; otherwise all other record fields
and payload are ignored.
There are two options for this device:
-global acpi-erst.size=X
-global acpi-erst.filename=Y
The size X, if not specified, defaults to 64KiB, and must be within
64KiB and 1MiB.
The filename Y, if not specified, defaults to "acpi-erst.backing".
The ERST backing storage is not mapped into the guest address space,
just the 8KiB programming area is mapped into the guest.
This has been utilized as a backend for the Linux pstore feature.
[1] ACPI 6.3 Specification, 18.3 Error Serialization
https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf
[2] UEFI 2.8 Specification, Appendix N Common Platform Error Record
https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_final.pdf