On Thu, 27 Feb 2025 12:03:49 +0100
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> wrote:
> While the HEST layout didn't change, there are some internal
> changes related to how offsets are calculated and how memory error
> events are triggered.
>
> Update specs to reflect such changes.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> ---
> docs/specs/acpi_hest_ghes.rst | 28 +++++++++++++++++-----------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/docs/specs/acpi_hest_ghes.rst b/docs/specs/acpi_hest_ghes.rst
> index c3e9f8d9a702..f3cb3074b082 100644
> --- a/docs/specs/acpi_hest_ghes.rst
> +++ b/docs/specs/acpi_hest_ghes.rst
> @@ -89,12 +89,21 @@ Design Details
> addresses in the "error_block_address" fields with a pointer to the
> respective "Error Status Data Block" in the "etc/hardware_errors" blob.
>
> -(8) QEMU defines a third and write-only fw_cfg blob which is called
> - "etc/hardware_errors_addr". Through that blob, the firmware can send back
> - the guest-side allocation addresses to QEMU. The "etc/hardware_errors_addr"
> - blob contains a 8-byte entry. QEMU generates a single WRITE_POINTER command
> - for the firmware. The firmware will write back the start address of
> - "etc/hardware_errors" blob to the fw_cfg file "etc/hardware_errors_addr".
> +(8) QEMU defines a third and write-only fw_cfg blob to store the location
> + where the error block offsets, read ack registers and CPER records are
> + stored.
> +
> + Up to QEMU 9.2, the location was at "etc/hardware_errors_addr", and
> + contains an offset for the beginning of "etc/hardware_errors".
s/^^^^/GPA/
> +
> + Newer versions place the location at "etc/acpi_table_hest_addr",
s/^^^^^^^^^^^/GPA or address/
> + pointing to the beginning of the HEST table.
> +
> + Through that such offsets, the firmware can send back the guest-side
^^^ see my previous s comment on that
> + allocation addresses to QEMU. They contain a 8-byte entry. QEMU generates
> + a single WRITE_POINTER command for the firmware. The firmware will write
> + back the start address of either "etc/hardware_errors" or HEST table at
> + the correspoinding address firmware.
^^^^^^^^^^^^^^^^ what is it?
perhaps it should be "fwcfg file"?
>
> (9) When QEMU gets a SIGBUS from the kernel, QEMU writes CPER into corresponding
> "Error Status Data Block", guest memory, and then injects platform specific
> @@ -105,8 +114,5 @@ Design Details
> kernel, on receiving notification, guest APEI driver could read the CPER error
> and take appropriate action.
>
> -(11) kvm_arch_on_sigbus_vcpu() uses source_id as index in "etc/hardware_errors" to
> - find out "Error Status Data Block" entry corresponding to error source. So supported
> - source_id values should be assigned here and not be changed afterwards to make sure
> - that guest will write error into expected "Error Status Data Block" even if guest was
> - migrated to a newer QEMU.
> +(11) kvm_arch_on_sigbus_vcpu() report RAS errors via a SEA notifications,
> + when a SIGBUS event is triggered.