Re: [PATCH v4 0/6] acpi: Error Record Serialization Table, ERST, support for QEMU

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 11 Jun 2021 14:31:17 -0400
Eric DeVolder <eric.devolder@oracle.com> wrote:

> 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. The size and location of the backing file is specified upon
> QEMU startup of the ACPI ERST device.
> 
> 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>
> 
> ---
> v4: 11jun2021
>  - Converted to a PCI device, per Igor.

Series looks much better now that impl. were split into
backend/frontend parts and dynamic MMIO placement.

I left some mandatory nit-picking about
comments, styles, overall documentation, leftovers
from previous revisions.
And also some how we can simplify impl. a bit more.


>  - Updated qtest.
> 
> v3: 28may2021
>  - Converted to using a TYPE_MEMORY_BACKEND_FILE object rather than
>    internal array with explicit file operations, per Igor.
>  - Changed the way the qdev and base address are handled, allowing
>    ERST to be disabled at run-time. Also aligns better with other
>    existing code.
> 
> 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 (6):
>   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: create ACPI ERST table for pc/x86 machines.
>   ACPI ERST: qtest for ERST
>   ACPI ERST: step 6 of bios-tables-test.c
> 
>  hw/acpi/erst.c               | 880 +++++++++++++++++++++++++++++++++++++++++++
>  hw/acpi/meson.build          |   1 +
>  hw/i386/acpi-build.c         |   5 +
>  include/hw/acpi/erst.h       |  79 ++++
>  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      | 109 ++++++
>  tests/qtest/meson.build      |   2 +
>  9 files changed, 1076 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
>