1.. SPDX-License-Identifier: GPL-2.0
2
3====================
4APEI Error INJection
5====================
6
7EINJ provides a hardware error injection mechanism. It is very useful
8for debugging and testing APEI and RAS features in general.
9
10You need to check whether your BIOS supports EINJ first. For that, look
11for early boot messages similar to this one::
12
13  ACPI: EINJ 0x000000007370A000 000150 (v01 INTEL           00000001 INTL 00000001)
14
15which shows that the BIOS is exposing an EINJ table - it is the
16mechanism through which the injection is done.
17
18Alternatively, look in /sys/firmware/acpi/tables for an "EINJ" file,
19which is a different representation of the same thing.
20
21It doesn't necessarily mean that EINJ is not supported if those above
22don't exist: before you give up, go into BIOS setup to see if the BIOS
23has an option to enable error injection. Look for something called WHEA
24or similar. Often, you need to enable an ACPI5 support option prior, in
25order to see the APEI,EINJ,... functionality supported and exposed by
26the BIOS menu.
27
28To use EINJ, make sure the following are options enabled in your kernel
29configuration::
30
31  CONFIG_DEBUG_FS
32  CONFIG_ACPI_APEI
33  CONFIG_ACPI_APEI_EINJ
34
35The EINJ user interface is in <debugfs mount point>/apei/einj.
36
37The following files belong to it:
38
39- available_error_type
40
41  This file shows which error types are supported:
42
43  ================  ===================================
44  Error Type Value	Error Description
45  ================  ===================================
46  0x00000001        Processor Correctable
47  0x00000002        Processor Uncorrectable non-fatal
48  0x00000004        Processor Uncorrectable fatal
49  0x00000008        Memory Correctable
50  0x00000010        Memory Uncorrectable non-fatal
51  0x00000020        Memory Uncorrectable fatal
52  0x00000040        PCI Express Correctable
53  0x00000080        PCI Express Uncorrectable non-fatal
54  0x00000100        PCI Express Uncorrectable fatal
55  0x00000200        Platform Correctable
56  0x00000400        Platform Uncorrectable non-fatal
57  0x00000800        Platform Uncorrectable fatal
58  ================  ===================================
59
60  The format of the file contents are as above, except present are only
61  the available error types.
62
63- error_type
64
65  Set the value of the error type being injected. Possible error types
66  are defined in the file available_error_type above.
67
68- error_inject
69
70  Write any integer to this file to trigger the error injection. Make
71  sure you have specified all necessary error parameters, i.e. this
72  write should be the last step when injecting errors.
73
74- flags
75
76  Present for kernel versions 3.13 and above. Used to specify which
77  of param{1..4} are valid and should be used by the firmware during
78  injection. Value is a bitmask as specified in ACPI5.0 spec for the
79  SET_ERROR_TYPE_WITH_ADDRESS data structure:
80
81    Bit 0
82      Processor APIC field valid (see param3 below).
83    Bit 1
84      Memory address and mask valid (param1 and param2).
85    Bit 2
86      PCIe (seg,bus,dev,fn) valid (see param4 below).
87
88  If set to zero, legacy behavior is mimicked where the type of
89  injection specifies just one bit set, and param1 is multiplexed.
90
91- param1
92
93  This file is used to set the first error parameter value. Its effect
94  depends on the error type specified in error_type. For example, if
95  error type is memory related type, the param1 should be a valid
96  physical memory address. [Unless "flag" is set - see above]
97
98- param2
99
100  Same use as param1 above. For example, if error type is of memory
101  related type, then param2 should be a physical memory address mask.
102  Linux requires page or narrower granularity, say, 0xfffffffffffff000.
103
104- param3
105
106  Used when the 0x1 bit is set in "flags" to specify the APIC id
107
108- param4
109  Used when the 0x4 bit is set in "flags" to specify target PCIe device
110
111- notrigger
112
113  The error injection mechanism is a two-step process. First inject the
114  error, then perform some actions to trigger it. Setting "notrigger"
115  to 1 skips the trigger phase, which *may* allow the user to cause the
116  error in some other context by a simple access to the CPU, memory
117  location, or device that is the target of the error injection. Whether
118  this actually works depends on what operations the BIOS actually
119  includes in the trigger phase.
120
121BIOS versions based on the ACPI 4.0 specification have limited options
122in controlling where the errors are injected. Your BIOS may support an
123extension (enabled with the param_extension=1 module parameter, or boot
124command line einj.param_extension=1). This allows the address and mask
125for memory injections to be specified by the param1 and param2 files in
126apei/einj.
127
128BIOS versions based on the ACPI 5.0 specification have more control over
129the target of the injection. For processor-related errors (type 0x1, 0x2
130and 0x4), you can set flags to 0x3 (param3 for bit 0, and param1 and
131param2 for bit 1) so that you have more information added to the error
132signature being injected. The actual data passed is this::
133
134	memory_address = param1;
135	memory_address_range = param2;
136	apicid = param3;
137	pcie_sbdf = param4;
138
139For memory errors (type 0x8, 0x10 and 0x20) the address is set using
140param1 with a mask in param2 (0x0 is equivalent to all ones). For PCI
141express errors (type 0x40, 0x80 and 0x100) the segment, bus, device and
142function are specified using param1::
143
144         31     24 23    16 15    11 10      8  7        0
145	+-------------------------------------------------+
146	| segment |   bus  | device | function | reserved |
147	+-------------------------------------------------+
148
149Anyway, you get the idea, if there's doubt just take a look at the code
150in drivers/acpi/apei/einj.c.
151
152An ACPI 5.0 BIOS may also allow vendor-specific errors to be injected.
153In this case a file named vendor will contain identifying information
154from the BIOS that hopefully will allow an application wishing to use
155the vendor-specific extension to tell that they are running on a BIOS
156that supports it. All vendor extensions have the 0x80000000 bit set in
157error_type. A file vendor_flags controls the interpretation of param1
158and param2 (1 = PROCESSOR, 2 = MEMORY, 4 = PCI). See your BIOS vendor
159documentation for details (and expect changes to this API if vendors
160creativity in using this feature expands beyond our expectations).
161
162
163An error injection example::
164
165  # cd /sys/kernel/debug/apei/einj
166  # cat available_error_type		# See which errors can be injected
167  0x00000002	Processor Uncorrectable non-fatal
168  0x00000008	Memory Correctable
169  0x00000010	Memory Uncorrectable non-fatal
170  # echo 0x12345000 > param1		# Set memory address for injection
171  # echo 0xfffffffffffff000 > param2		# Mask - anywhere in this page
172  # echo 0x8 > error_type			# Choose correctable memory error
173  # echo 1 > error_inject			# Inject now
174
175You should see something like this in dmesg::
176
177  [22715.830801] EDAC sbridge MC3: HANDLING MCE MEMORY ERROR
178  [22715.834759] EDAC sbridge MC3: CPU 0: Machine Check Event: 0 Bank 7: 8c00004000010090
179  [22715.834759] EDAC sbridge MC3: TSC 0
180  [22715.834759] EDAC sbridge MC3: ADDR 12345000 EDAC sbridge MC3: MISC 144780c86
181  [22715.834759] EDAC sbridge MC3: PROCESSOR 0:306e7 TIME 1422553404 SOCKET 0 APIC 0
182  [22716.616173] EDAC MC3: 1 CE memory read error on CPU_SrcID#0_Channel#0_DIMM#0 (channel:0 slot:0 page:0x12345 offset:0x0 grain:32 syndrome:0x0 -  area:DRAM err_code:0001:0090 socket:0 channel_mask:1 rank:0)
183
184Special notes for injection into SGX enclaves:
185
186There may be a separate BIOS setup option to enable SGX injection.
187
188The injection process consists of setting some special memory controller
189trigger that will inject the error on the next write to the target
190address. But the h/w prevents any software outside of an SGX enclave
191from accessing enclave pages (even BIOS SMM mode).
192
193The following sequence can be used:
194  1) Determine physical address of enclave page
195  2) Use "notrigger=1" mode to inject (this will setup
196     the injection address, but will not actually inject)
197  3) Enter the enclave
198  4) Store data to the virtual address matching physical address from step 1
199  5) Execute CLFLUSH for that virtual address
200  6) Spin delay for 250ms
201  7) Read from the virtual address. This will trigger the error
202
203For more information about EINJ, please refer to ACPI specification
204version 4.0, section 17.5 and ACPI 5.0, section 18.6.
205