stubs: Move qemu_timer_notify_cb() and remove qemu_notify_event() stub
[qemu.git] / docs / specs / acpi_hest_ghes.rst
1 APEI tables generating and CPER record
2 ======================================
3
4 ..
5    Copyright (c) 2020 HUAWEI TECHNOLOGIES CO., LTD.
6
7    This work is licensed under the terms of the GNU GPL, version 2 or later.
8    See the COPYING file in the top-level directory.
9
10 Design Details
11 --------------
12
13 ::
14
15          etc/acpi/tables                           etc/hardware_errors
16       ====================                   ===============================
17   + +--------------------------+            +----------------------------+
18   | | HEST                     | +--------->|    error_block_address1    |------+
19   | +--------------------------+ |          +----------------------------+      |
20   | | GHES1                    | | +------->|    error_block_address2    |------+-+
21   | +--------------------------+ | |        +----------------------------+      | |
22   | | .................        | | |        |      ..............        |      | |
23   | | error_status_address-----+-+ |        -----------------------------+      | |
24   | | .................        |   |   +--->|    error_block_addressN    |------+-+---+
25   | | read_ack_register--------+-+ |   |    +----------------------------+      | |   |
26   | | read_ack_preserve        | +-+---+--->|     read_ack_register1     |      | |   |
27   | | read_ack_write           |   |   |    +----------------------------+      | |   |
28   + +--------------------------+   | +-+--->|     read_ack_register2     |      | |   |
29   | | GHES2                    |   | | |    +----------------------------+      | |   |
30   + +--------------------------+   | | |    |       .............        |      | |   |
31   | | .................        |   | | |    +----------------------------+      | |   |
32   | | error_status_address-----+---+ | | +->|     read_ack_registerN     |      | |   |
33   | | .................        |     | | |  +----------------------------+      | |   |
34   | | read_ack_register--------+-----+ | |  |Generic Error Status Block 1|<-----+ |   |
35   | | read_ack_preserve        |       | |  |-+------------------------+-+        |   |
36   | | read_ack_write           |       | |  | |          CPER          | |        |   |
37   + +--------------------------|       | |  | |          CPER          | |        |   |
38   | | ...............          |       | |  | |          ....          | |        |   |
39   + +--------------------------+       | |  | |          CPER          | |        |   |
40   | | GHESN                    |       | |  |-+------------------------+-|        |   |
41   + +--------------------------+       | |  |Generic Error Status Block 2|<-------+   |
42   | | .................        |       | |  |-+------------------------+-+            |
43   | | error_status_address-----+-------+ |  | |           CPER         | |            |
44   | | .................        |         |  | |           CPER         | |            |
45   | | read_ack_register--------+---------+  | |           ....         | |            |
46   | | read_ack_preserve        |            | |           CPER         | |            |
47   | | read_ack_write           |            +-+------------------------+-+            |
48   + +--------------------------+            |         ..........         |            |
49                                             |----------------------------+            |
50                                             |Generic Error Status Block N |<----------+
51                                             |-+-------------------------+-+
52                                             | |          CPER           | |
53                                             | |          CPER           | |
54                                             | |          ....           | |
55                                             | |          CPER           | |
56                                             +-+-------------------------+-+
57
58
59 (1) QEMU generates the ACPI HEST table. This table goes in the current
60     "etc/acpi/tables" fw_cfg blob. Each error source has different
61     notification types.
62
63 (2) A new fw_cfg blob called "etc/hardware_errors" is introduced. QEMU
64     also needs to populate this blob. The "etc/hardware_errors" fw_cfg blob
65     contains an address registers table and an Error Status Data Block table.
66
67 (3) The address registers table contains N Error Block Address entries
68     and N Read Ack Register entries. The size for each entry is 8-byte.
69     The Error Status Data Block table contains N Error Status Data Block
70     entries. The size for each entry is 4096(0x1000) bytes. The total size
71     for the "etc/hardware_errors" fw_cfg blob is (N * 8 * 2 + N * 4096) bytes.
72     N is the number of the kinds of hardware error sources.
73
74 (4) QEMU generates the ACPI linker/loader script for the firmware. The
75     firmware pre-allocates memory for "etc/acpi/tables", "etc/hardware_errors"
76     and copies blob contents there.
77
78 (5) QEMU generates N ADD_POINTER commands, which patch addresses in the
79     "error_status_address" fields of the HEST table with a pointer to the
80     corresponding "address registers" in the "etc/hardware_errors" blob.
81
82 (6) QEMU generates N ADD_POINTER commands, which patch addresses in the
83     "read_ack_register" fields of the HEST table with a pointer to the
84     corresponding "read_ack_register" within the "etc/hardware_errors" blob.
85
86 (7) QEMU generates N ADD_POINTER commands for the firmware, which patch
87     addresses in the "error_block_address" fields with a pointer to the
88     respective "Error Status Data Block" in the "etc/hardware_errors" blob.
89
90 (8) QEMU defines a third and write-only fw_cfg blob which is called
91     "etc/hardware_errors_addr". Through that blob, the firmware can send back
92     the guest-side allocation addresses to QEMU. The "etc/hardware_errors_addr"
93     blob contains a 8-byte entry. QEMU generates a single WRITE_POINTER command
94     for the firmware. The firmware will write back the start address of
95     "etc/hardware_errors" blob to the fw_cfg file "etc/hardware_errors_addr".
96
97 (9) When QEMU gets a SIGBUS from the kernel, QEMU writes CPER into corresponding
98     "Error Status Data Block", guest memory, and then injects platform specific
99     interrupt (in case of arm/virt machine it's Synchronous External Abort) as a
100     notification which is necessary for notifying the guest.
101
102 (10) This notification (in virtual hardware) will be handled by the guest
103      kernel, on receiving notification, guest APEI driver could read the CPER error
104      and take appropriate action.
105
106 (11) kvm_arch_on_sigbus_vcpu() uses source_id as index in "etc/hardware_errors" to
107      find out "Error Status Data Block" entry corresponding to error source. So supported
108      source_id values should be assigned here and not be changed afterwards to make sure
109      that guest will write error into expected "Error Status Data Block" even if guest was
110      migrated to a newer QEMU.