docs: APEI GHES generation and CPER record description

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>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Message-id: 20200512030609.19593-4-gengdongjiu@huawei.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 111 insertions, 0 deletions

diff --git a/docs/specs/acpi_hest_ghes.rst b/docs/specs/acpi_hest_ghes.rst
new file mode 100644
index 0000000000..68f1fbe0a4
--- /dev/null
+++ b/docs/specs/acpi_hest_ghes.rst
@@ -0,0 +1,110 @@
+APEI tables generating and CPER record
+======================================
+
+..
+   Copyright (c) 2020 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                     | +--------->|    error_block_address1    |------+
+  | +--------------------------+ |          +----------------------------+      |
+  | | GHES1                    | | +------->|    error_block_address2    |------+-+
+  | +--------------------------+ | |        +----------------------------+      | |
+  | | .................        | | |        |      ..............        |      | |
+  | | error_status_address-----+-+ |        -----------------------------+      | |
+  | | .................        |   |   +--->|    error_block_addressN    |------+-+---+
+  | | read_ack_register--------+-+ |   |    +----------------------------+      | |   |
+  | | read_ack_preserve        | +-+---+--->|     read_ack_register1     |      | |   |
+  | | read_ack_write           |   |   |    +----------------------------+      | |   |
+  + +--------------------------+   | +-+--->|     read_ack_register2     |      | |   |
+  | | GHES2                    |   | | |    +----------------------------+      | |   |
+  + +--------------------------+   | | |    |       .............        |      | |   |
+  | | .................        |   | | |    +----------------------------+      | |   |
+  | | error_status_address-----+---+ | | +->|     read_ack_registerN     |      | |   |
+  | | .................        |     | | |  +----------------------------+      | |   |
+  | | read_ack_register--------+-----+ | |  |Generic Error Status Block 1|<-----+ |   |
+  | | read_ack_preserve        |       | |  |-+------------------------+-+        |   |
+  | | read_ack_write           |       | |  | |          CPER          | |        |   |
+  + +--------------------------|       | |  | |          CPER          | |        |   |
+  | | ...............          |       | |  | |          ....          | |        |   |
+  + +--------------------------+       | |  | |          CPER          | |        |   |
+  | | GHESN                    |       | |  |-+------------------------+-|        |   |
+  + +--------------------------+       | |  |Generic Error Status Block 2|<-------+   |
+  | | .................        |       | |  |-+------------------------+-+            |
+  | | error_status_address-----+-------+ |  | |           CPER         | |            |
+  | | .................        |         |  | |           CPER         | |            |
+  | | read_ack_register--------+---------+  | |           ....         | |            |
+  | | read_ack_preserve        |            | |           CPER         | |            |
+  | | read_ack_write           |            +-+------------------------+-+            |
+  + +--------------------------+            |         ..........         |            |
+                                            |----------------------------+            |
+                                            |Generic Error Status Block N |<----------+
+                                            |-+-------------------------+-+
+                                            | |          CPER           | |
+                                            | |          CPER           | |
+                                            | |          ....           | |
+                                            | |          CPER           | |
+                                            +-+-------------------------+-+
+
+
+(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 "read_ack_register" within the "etc/hardware_errors" blob.
+
+(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 writes CPER into corresponding
+    "Error Status Data Block", guest memory, 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, 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.
diff --git a/docs/specs/index.rst b/docs/specs/index.rst
index de46a8b5e7..426632a475 100644
--- a/docs/specs/index.rst
+++ b/docs/specs/index.rst
@@ -14,3 +14,4 @@ Contents:
    ppc-spapr-xive
    acpi_hw_reduced_hotplug
    tpm
+   acpi_hest_ghes