[PATCH v2 0/7] acpi: Error Record Serialization Table, ERST, support for QEMU

[Eric DeVolder]

This patchset introduces support for the ACPI Error Record
Serialization Table, ERST.

Linux uses the persistent storage filesystem, pstore, to record
information (eg. dmesg tail) upon panics and shutdowns.  Pstore is
independent of, and runs before, kdump.  In certain scenarios (ie.
hosts/guests with root filesystems on NFS/iSCSI where networking
software and/or hardware fails), pstore may contain the only
information available for post-mortem debugging.

Two common storage backends for the pstore filesystem are ACPI ERST
and UEFI. Most BIOS implement ACPI ERST; however, ACPI ERST is not
currently supported in QEMU, and UEFI is not utilized in all guests.
By implementing ACPI ERST within QEMU, then the ACPI ERST becomes a
viable pstore storage backend for virtual machines (as it is now for
bare metal machines).

Enabling support for ACPI ERST facilitates a consistent method to
capture kernel panic information in a wide range of guests: from
resource- constrained microvms to very large guests, and in
particular, in direct-boot environments (which would lack UEFI
run-time services).

Note that Microsoft Windows also utilizes the ACPI ERST for certain
crash information, if available.

The ACPI ERST persistent storage is contained within a single backing
file, with a default size of 64KiB. The size and filename of the
backing file can be obtained from QEMU parameters.

The ACPI specification[1], in Chapter "ACPI Platform Error Interfaces
(APEI)", and specifically subsection "Error Serialization", outlines
a method for storing error records into persistent storage.

[1] "Advanced Configuration and Power Interface Specification",
    version 6.2, May 2017.
    https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf

[2] "Unified Extensible Firmware Interface Specification",
    version 2.8, March 2019.
    https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_final.pdf

Suggested-by: Konrad Wilk <konrad.wilk@oracle.com>
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>

---
v2: 8feb2021
 - Added qtest/smoke test per Paolo Bonzini
 - Split patch into smaller chunks, per Igo Mammedov
 - Did away with use of ACPI packed structures, per Igo Mammedov

v1: 26oct2020
 - initial post

---
Eric DeVolder (7):
  ACPI ERST: bios-tables-test.c steps 1 and 2
  ACPI ERST: header file for erst
  ACPI ERST: support for ACPI ERST feature
  ACPI ERST: build step for ACPI ERST
  ACPI ERST: support ERST for x86 guest
  ACPI ERST: qtest for ERST
  ACPI ERST: bios-tables-test.c step 5

 hw/acpi/erst.c               | 952 +++++++++++++++++++++++++++++++++++++++++++
 hw/acpi/meson.build          |   1 +
 hw/i386/acpi-build.c         |   4 +
 include/hw/acpi/erst.h       |  77 ++++
 tests/data/acpi/microvm/ERST |   0
 tests/data/acpi/pc/ERST      | Bin 0 -> 976 bytes
 tests/data/acpi/q35/ERST     | Bin 0 -> 976 bytes
 tests/qtest/erst-test.c      | 106 +++++
 tests/qtest/meson.build      |   2 +
 9 files changed, 1142 insertions(+)
 create mode 100644 hw/acpi/erst.c
 create mode 100644 include/hw/acpi/erst.h
 create mode 100644 tests/data/acpi/microvm/ERST
 create mode 100644 tests/data/acpi/pc/ERST
 create mode 100644 tests/data/acpi/q35/ERST
 create mode 100644 tests/qtest/erst-test.c

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1.8.3.1