			APEI Error INJection
			~~~~~~~~~~~~~~~~~~~~

EINJ provides a hardware error injection mechanism
It is very useful for debugging and testing of other APEI and RAS features.

To use EINJ, make sure the following are enabled in your kernel
configuration:

CONFIG_DEBUG_FS
CONFIG_ACPI_APEI
CONFIG_ACPI_APEI_EINJ

The user interface of EINJ is debug file system, under the
directory apei/einj. The following files are provided.

- available_error_type
  Reading this file returns the error injection capability of the
  platform, that is, which error types are supported. The error type
  definition is as follow, the left field is the error type value, the
  right field is error description.

    0x00000001	Processor Correctable
    0x00000002	Processor Uncorrectable non-fatal
    0x00000004	Processor Uncorrectable fatal
    0x00000008  Memory Correctable
    0x00000010  Memory Uncorrectable non-fatal
    0x00000020  Memory Uncorrectable fatal
    0x00000040	PCI Express Correctable
    0x00000080	PCI Express Uncorrectable fatal
    0x00000100	PCI Express Uncorrectable non-fatal
    0x00000200	Platform Correctable
    0x00000400	Platform Uncorrectable non-fatal
    0x00000800	Platform Uncorrectable fatal

  The format of file contents are as above, except there are only the
  available error type lines.

- error_type
  This file is used to set the error type value. The error type value
  is defined in "available_error_type" description.

- error_inject
  Write any integer to this file to trigger the error
  injection. Before this, please specify all necessary error
  parameters.

- flags
  Present for kernel version 3.13 and above. Used to specify which
  of param{1..4} are valid and should be used by BIOS during injection.
  Value is a bitmask as specified in ACPI5.0 spec for the
  SET_ERROR_TYPE_WITH_ADDRESS data structure:
	Bit 0 - Processor APIC field valid (see param3 below)
	Bit 1 - Memory address and mask valid (param1 and param2)
	Bit 2 - PCIe (seg,bus,dev,fn) valid (param4 below)
  If set to zero, legacy behaviour is used where the type of injection
  specifies just one bit set, and param1 is multiplexed.

- param1
  This file is used to set the first error parameter value. Effect of
  parameter depends on error_type specified.

- param2
  This file is used to set the second error parameter value. Effect of
  parameter depends on error_type specified.

- param3
  Used when the 0x1 bit is set in "flag" to specify the APIC id

- param4
  Used when the 0x4 bit is set in "flag" to specify target PCIe device

- notrigger
  The EINJ mechanism is a two step process. First inject the error, then
  perform some actions to trigger it. Setting "notrigger" to 1 skips the
  trigger phase, which *may* allow the user to cause the error in some other
  context by a simple access to the cpu, memory location, or device that is
  the target of the error injection. Whether this actually works depends
  on what operations the BIOS actually includes in the trigger phase.

BIOS versions based in the ACPI 4.0 specification have limited options
to control where the errors are injected.  Your BIOS may support an
extension (enabled with the param_extension=1 module parameter, or
boot command line einj.param_extension=1). This allows the address
and mask for memory injections to be specified by the param1 and
param2 files in apei/einj.

BIOS versions using the ACPI 5.0 specification have more control over
the target of the injection. For processor related errors (type 0x1,
0x2 and 0x4) the APICID of the target should be provided using the
param1 file in apei/einj. For memory errors (type 0x8, 0x10 and 0x20)
the address is set using param1 with a mask in param2 (0x0 is equivalent
to all ones). For PCI express errors (type 0x40, 0x80 and 0x100) the
segment, bus, device and function are specified using param1:

         31     24 23    16 15    11 10      8  7        0
	+-------------------------------------------------+
	| segment |   bus  | device | function | reserved |
	+-------------------------------------------------+

An ACPI 5.0 BIOS may also allow vendor specific errors to be injected.
In this case a file named vendor will contain identifying information
from the BIOS that hopefully will allow an application wishing to use
the vendor specific extension to tell that they are running on a BIOS
that supports it. All vendor extensions have the 0x80000000 bit set in
error_type. A file vendor_flags controls the interpretation of param1
and param2 (1 = PROCESSOR, 2 = MEMORY, 4 = PCI). See your BIOS vendor
documentation for details (and expect changes to this API if vendors
creativity in using this feature expands beyond our expectations).

Example:
# cd /sys/kernel/debug/apei/einj
# cat available_error_type		# See which errors can be injected
0x00000002	Processor Uncorrectable non-fatal
0x00000008	Memory Correctable
0x00000010	Memory Uncorrectable non-fatal
# echo 0x12345000 > param1		# Set memory address for injection
# echo 0xfffffffffffff000 > param2	# Mask - anywhere in this page
# echo 0x8 > error_type			# Choose correctable memory error
# echo 1 > error_inject			# Inject now


For more information about EINJ, please refer to ACPI specification
version 4.0, section 17.5 and ACPI 5.0, section 18.6.
