new file mode 100644
@@ -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.
@@ -14,3 +14,4 @@ Contents:
ppc-spapr-xive
acpi_hw_reduced_hotplug
tpm
+ acpi_hest_ghes