Re: [RESEND PATCH v21 2/6] docs: APEI GHES generation and CPER record description

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 11 Nov 2019 09:40:44 +0800
Xiang Zheng <zhengxiang9@huawei.com> wrote:

> From: Dongjiu Geng <gengdongjiu@huawei.com>
> 
> Add APEI/GHES detailed design document
> 
> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
> Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  docs/specs/acpi_hest_ghes.rst | 95 +++++++++++++++++++++++++++++++++++
>  docs/specs/index.rst          |  1 +
>  2 files changed, 96 insertions(+)
>  create mode 100644 docs/specs/acpi_hest_ghes.rst
> 
> diff --git a/docs/specs/acpi_hest_ghes.rst b/docs/specs/acpi_hest_ghes.rst
> new file mode 100644
> index 0000000000..348825f9d3
> --- /dev/null
> +++ b/docs/specs/acpi_hest_ghes.rst
> @@ -0,0 +1,95 @@
> +APEI tables generating and CPER record
> +======================================
> +
> +..
> +   Copyright (c) 2019 HUAWEI TECHNOLOGIES CO., LTD.
> +
> +   This work is licensed under the terms of the GNU GPL, version 2 or later.
> +   See the COPYING file in the top-level directory.
> +
> +Design Details
> +--------------
> +
> +::
> +
> +         etc/acpi/tables                                 etc/hardware_errors
> +      ====================                      ==========================================
> +  + +--------------------------+            +-----------------------+
> +  | | HEST                     |            |    address            |            +--------------+
> +  | +--------------------------+            |    registers          |            | Error Status |
> +  | | GHES1                    |            | +---------------------+            | Data Block 1 |
> +  | +--------------------------+ +--------->| |error_block_address1 |----------->| +------------+
> +  | | .................        | |          | +---------------------+            | |  CPER      |
> +  | | error_status_address-----+-+ +------->| |error_block_address2 |--------+   | |  CPER      |
> +  | | .................        |   |        | +---------------------+        |   | |  ....      |
> +  | | read_ack_register--------+-+ |        | |    ..............   |        |   | |  CPER      |
> +  | | read_ack_preserve        | | |        +-----------------------+        |   | +------------+
> +  | | read_ack_write           | | | +----->| |error_block_addressN |------+ |   | Error Status |
> +  + +--------------------------+ | | |      | +---------------------+      | |   | Data Block 2 |
> +  | | GHES2                    | +-+-+----->| |read_ack_register1   |      | +-->| +------------+
> +  + +--------------------------+   | |      | +---------------------+      |     | |  CPER      |
> +  | | .................        |   | | +--->| |read_ack_register2   |      |     | |  CPER      |
> +  | | error_status_address-----+---+ | |    | +---------------------+      |     | |  ....      |
> +  | | .................        |     | |    | |  .............      |      |     | |  CPER      |
> +  | | read_ack_register--------+-----+-+    | +---------------------+      |     +-+------------+
> +  | | read_ack_preserve        |     |   +->| |read_ack_registerN   |      |     | |..........  |
> +  | | read_ack_write           |     |   |  | +---------------------+      |     | +------------+
> +  + +--------------------------|     |   |                                 |     | Error Status |
> +  | | ...............          |     |   |                                 |     | Data Block N |
> +  + +--------------------------+     |   |                                 +---->| +------------+
> +  | | GHESN                    |     |   |                                       | |  CPER      |
> +  + +--------------------------+     |   |                                       | |  CPER      |
> +  | | .................        |     |   |                                       | |  ....      |
> +  | | error_status_address-----+-----+   |                                       | |  CPER      |
> +  | | .................        |         |                                       +-+------------+
> +  | | read_ack_register--------+---------+
> +  | | read_ack_preserve        |
> +  | | read_ack_write           |
> +  + +--------------------------+

I'd merge "Error Status Data Block" with "address registers", so it would be
clear that "Error Status Data Block" is located after "read_ack_registerN"

> +
> +(1) QEMU generates the ACPI HEST table. This table goes in the current
> +    "etc/acpi/tables" fw_cfg blob. Each error source has different
> +    notification types.
> +
> +(2) A new fw_cfg blob called "etc/hardware_errors" is introduced. QEMU
> +    also needs to populate this blob. The "etc/hardware_errors" fw_cfg blob
> +    contains an address registers table and an Error Status Data Block table.
> +
> +(3) The address registers table contains N Error Block Address entries
> +    and N Read Ack Register entries. The size for each entry is 8-byte.
> +    The Error Status Data Block table contains N Error Status Data Block
> +    entries. The size for each entry is 4096(0x1000) bytes. The total size
> +    for the "etc/hardware_errors" fw_cfg blob is (N * 8 * 2 + N * 4096) bytes.
> +    N is the number of the kinds of hardware error sources.
> +
> +(4) QEMU generates the ACPI linker/loader script for the firmware. The
> +    firmware pre-allocates memory for "etc/acpi/tables", "etc/hardware_errors"
> +    and copies blob contents there.
> +
> +(5) QEMU generates N ADD_POINTER commands, which patch addresses in the
> +    "error_status_address" fields of the HEST table with a pointer to the
> +    corresponding "address registers" in the "etc/hardware_errors" blob.
> +
> +(6) QEMU generates N ADD_POINTER commands, which patch addresses in the
> +    "read_ack_register" fields of the HEST table with a pointer to the
> +    corresponding "address registers" in the "etc/hardware_errors" blob.

s/"address registers" in/"read_ack_register" within/

> +
> +(7) QEMU generates N ADD_POINTER commands for the firmware, which patch
> +    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".
> +

> +(9) When QEMU gets a SIGBUS from the kernel, QEMU formats the CPER right into
> +    guest memory, 

s/
QEMU formats the CPER right into guest memory
/
QEMU writes CPER into corresponding "Error Status Data Block"
/

> and then injects platform specific interrupt (in case of
> +    arm/virt machine it's Synchronous External Abort) as a notification which
> +    is necessary for notifying the guest.


> +
> +(10) This notification (in virtual hardware) will be handled by the guest
> +     kernel, guest APEI driver will read the CPER which is recorded by QEMU and
> +     do the recovery.
Maybe better would be to say:
"
On receiving notification, guest APEI driver cold read the CPER error
and take appropriate action
"


also in HEST patches there is implicit ABI, which probably should be documented here.
More specifically kvm_arch_on_sigbus_vcpu() error injection
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.


> diff --git a/docs/specs/index.rst b/docs/specs/index.rst
> index 984ba44029..3019b9c976 100644
> --- a/docs/specs/index.rst
> +++ b/docs/specs/index.rst
> @@ -13,3 +13,4 @@ Contents:
>     ppc-xive
>     ppc-spapr-xive
>     acpi_hw_reduced_hotplug
> +   acpi_hest_ghes