Documentation/acpi/einj: Correct and streamline text

Streamline and simplify formulations, improve formatting and extend the
injection example in the error injection write up for users which we
carry in Documentation/.

Add a paragraph about checking for EINJ support and expand the ACPI5.0
memory errors section, as requested by Tony.
Acked-by: NTony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/1422553845-30717-1-git-send-email-bp@alien8.deSigned-off-by: NBorislav Petkov <bp@suse.de>

Documentation/acpi/apei/einj.txt

 			APEI Error INJection
 			~~~~~~~~~~~~~~~~~~~~
 
-EINJ provides a hardware error injection mechanism
-It is very useful for debugging and testing of other APEI and RAS features.
+EINJ provides a hardware error injection mechanism. It is very useful
+for debugging and testing APEI and RAS features in general.
 
-To use EINJ, make sure the following are enabled in your kernel
+You need to check whether your BIOS supports EINJ first. For that, look
+for early boot messages similar to this one:
+
+ACPI: EINJ 0x000000007370A000 000150 (v01 INTEL           00000001 INTL 00000001)
+
+which shows that the BIOS is exposing an EINJ table - it is the
+mechanism through which the injection is done.
+
+Alternatively, look in /sys/firmware/acpi/tables for an "EINJ" file,
+which is a different representation of the same thing.
+
+It doesn't necessarily mean that EINJ is not supported if those above
+don't exist: before you give up, go into BIOS setup to see if the BIOS
+has an option to enable error injection. Look for something called WHEA
+or similar. Often, you need to enable an ACPI5 support option prior, in
+order to see the APEI,EINJ,... functionality supported and exposed by
+the BIOS menu.
+
+To use EINJ, make sure the following are options 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.
+The EINJ user interface is in <debugfs mount point>/apei/einj.
+
+The following files belong to it:
 
 - 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.
+
+  This file shows which error types are supported:
+
+  Error Type Value	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 the file contents are as above, except present are only
+  the available error types.
 
 - error_type
-  This file is used to set the error type value. The error type value
-  is defined in "available_error_type" description.
+
+  Set the value of the error type being injected. Possible error types
+  are defined in the file available_error_type above.
 
 - error_inject
-  Write any integer to this file to trigger the error
-  injection. Before this, please specify all necessary error
-  parameters.
+
+  Write any integer to this file to trigger the error injection. Make
+  sure you have specified all necessary error parameters, i.e. this
+  write should be the last step when injecting errors.
 
 - 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
+
+  Present for kernel versions 3.13 and above. Used to specify which
+  of param{1..4} are valid and should be used by the firmware 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.
+
+	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 (see param4 below).
+
+  If set to zero, legacy behavior is mimicked 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. For example, if error
-  type is memory related type, the param1 should be a valid physical
-  memory address. [Unless "flag" is set - see above]
+
+  This file is used to set the first error parameter value. Its effect
+  depends on the error type specified in error_type. For example, if
+  error type is memory related type, the param1 should be a valid
+  physical memory address. [Unless "flag" is set - see above]
 
 - param2
-  This file is used to set the second error parameter value. Effect of
-  parameter depends on error_type specified. For example, if error
-  type is memory related type, the param2 should be a physical memory
-  address mask. Linux requires page or narrower granularity, say,
-  0xfffffffffffff000.
+
+  Same use as param1 above. For example, if error type is of memory
+  related type, then param2 should be a physical memory address mask.
+  Linux requires page or narrower granularity, say, 0xfffffffffffff000.
 
 - param3
-  Used when the 0x1 bit is set in "flag" to specify the APIC id
+
+  Used when the 0x1 bit is set in "flags" to specify the APIC id
 
 - param4
-  Used when the 0x4 bit is set in "flag" to specify target PCIe device
+  Used when the 0x4 bit is set in "flags" 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:
+
+  The error injection 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 on the ACPI 4.0 specification have limited options
+in controlling 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 based on the ACPI 5.0 specification have more control over
+the target of the injection. For processor-related errors (type 0x1, 0x2
+and 0x4), you can set flags to 0x3 (param3 for bit 0, and param1 and
+param2 for bit 1) so that you have more information added to the error
+signature being injected. The actual data passed is this:
+
+	memory_address = param1;
+	memory_address_range = param2;
+	apicid = param3;
+	pcie_sbdf = param4;
+
+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.
+Anyway, you get the idea, if there's doubt just take a look at the code
+in drivers/acpi/apei/einj.c.
+
+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
+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:
+
+An error injection 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 $((-1 << 12)) > param2		# Mask 0xfffffffffffff000 - anywhere in this page
 # echo 0x8 > error_type			# Choose correctable memory error
 # echo 1 > error_inject			# Inject now
 
+You should see something like this in dmesg:
+
+[22715.830801] EDAC sbridge MC3: HANDLING MCE MEMORY ERROR
+[22715.834759] EDAC sbridge MC3: CPU 0: Machine Check Event: 0 Bank 7: 8c00004000010090
+[22715.834759] EDAC sbridge MC3: TSC 0
+[22715.834759] EDAC sbridge MC3: ADDR 12345000 EDAC sbridge MC3: MISC 144780c86
+[22715.834759] EDAC sbridge MC3: PROCESSOR 0:306e7 TIME 1422553404 SOCKET 0 APIC 0
+[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)
 
 For more information about EINJ, please refer to ACPI specification
 version 4.0, section 17.5 and ACPI 5.0, section 18.6.