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diff --git a/Documentation/admin-guide/ras.rst b/Documentation/admin-guide/ras.rst new file mode 100644 index 000000000000..d71340e86c27 --- /dev/null +++ b/Documentation/admin-guide/ras.rst @@ -0,0 +1,1190 @@ +.. include:: <isonum.txt> + +============================================ +Reliability, Availability and Serviceability +============================================ + +RAS concepts +************ + +Reliability, Availability and Serviceability (RAS) is a concept used on +servers meant to measure their robusteness. + +Reliability + is the probability that a system will produce correct outputs. + + * Generally measured as Mean Time Between Failures (MTBF) + * Enhanced by features that help to avoid, detect and repair hardware faults + +Availability + is the probability that a system is operational at a given time + + * Generally measured as a percentage of downtime per a period of time + * Often uses mechanisms to detect and correct hardware faults in + runtime; + +Serviceability (or maintainability) + is the simplicity and speed with which a system can be repaired or + maintained + + * Generally measured on Mean Time Between Repair (MTBR) + +Improving RAS +------------- + +In order to reduce systems downtime, a system should be capable of detecting +hardware errors, and, when possible correcting them in runtime. It should +also provide mechanisms to detect hardware degradation, in order to warn +the system administrator to take the action of replacing a component before +it causes data loss or system downtime. + +Among the monitoring measures, the most usual ones include: + +* CPU – detect errors at instruction execution and at L1/L2/L3 caches; +* Memory – add error correction logic (ECC) to detect and correct errors; +* I/O – add CRC checksums for tranfered data; +* Storage – RAID, journal file systems, checksums, + Self-Monitoring, Analysis and Reporting Technology (SMART). + +By monitoring the number of occurrences of error detections, it is possible +to identify if the probability of hardware errors is increasing, and, on such +case, do a preventive maintainance to replace a degrated component while +those errors are correctable. + +Types of errors +--------------- + +Most mechanisms used on modern systems use use technologies like Hamming +Codes that allow error correction when the number of errors on a bit packet +is below a threshold. If the number of errors is above, those mechanisms +can indicate with a high degree of confidence that an error happened, but +they can't correct. + +Also, sometimes an error occur on a component that it is not used. For +example, a part of the memory that it is not currently allocated. + +That defines some categories of errors: + +* **Correctable Error (CE)** - the error detection mechanism detected and + corrected the error. Such errors are usually not fatal, although some + Kernel mechanisms allow the system administrator to consider them as fatal. + +* **Uncorrected Error (UE)** - the amount of errors happened above the error + correction threshold, and the system was unable to auto-correct. + +* **Fatal Error** - when an UE error happens on a critical component of the + system (for example, a piece of the Kernel got corrupted by an UE), the + only reliable way to avoid data corruption is to hang or reboot the machine. + +* **Non-fatal Error** - when an UE error happens on an unused component, + like a CPU in power down state or an unused memory bank, the system may + still run, eventually replacing the affected hardware by a hot spare, + if available. + + Also, when an error happens on an userspace process, it is also possible to + kill such process and let userspace restart it. + +The mechanism for handling non-fatal errors is usually complex and may +require the help of some userspace application, in order to apply the +policy desired by the system administrator. + +Identifying a bad hardware component +------------------------------------ + +Just detecting a hardware flaw is usually not enough, as the system needs +to pinpoint to the minimal replaceable unit (MRU) that should be exchanged +to make the hardware reliable again. + +So, it requires not only error logging facilities, but also mechanisms that +will translate the error message to the silkscreen or component label for +the MRU. + +Typically, it is very complex for memory, as modern CPUs interlace memory +from different memory modules, in order to provide a better performance. The +DMI BIOS usually have a list of memory module labels, with can be obtained +using the ``dmidecode`` tool. For example, on a desktop machine, it shows:: + + Memory Device + Total Width: 64 bits + Data Width: 64 bits + Size: 16384 MB + Form Factor: SODIMM + Set: None + Locator: ChannelA-DIMM0 + Bank Locator: BANK 0 + Type: DDR4 + Type Detail: Synchronous + Speed: 2133 MHz + Rank: 2 + Configured Clock Speed: 2133 MHz + +On the above example, a DDR4 SO-DIMM memory module is located at the +system's memory labeled as "BANK 0", as given by the *bank locator* field. +Please notice that, on such system, the *total width* is equal to the +*data witdh*. It means that such memory module doesn't have error +detection/correction mechanisms. + +Unfortunately, not all systems use the same field to specify the memory +bank. On this example, from an older server, ``dmidecode`` shows:: + + Memory Device + Array Handle: 0x1000 + Error Information Handle: Not Provided + Total Width: 72 bits + Data Width: 64 bits + Size: 8192 MB + Form Factor: DIMM + Set: 1 + Locator: DIMM_A1 + Bank Locator: Not Specified + Type: DDR3 + Type Detail: Synchronous Registered (Buffered) + Speed: 1600 MHz + Rank: 2 + Configured Clock Speed: 1600 MHz + +There, the DDR3 RDIMM memory module is located at the system's memory labeled +as "DIMM_A1", as given by the *locator* field. Please notice that this +memory module has 64 bits of *data witdh* and 72 bits of *total width*. So, +it has 8 extra bits to be used by error detection and correction mechanisms. +Such kind of memory is called Error-correcting code memory (ECC memory). + +To make things even worse, it is not uncommon that systems with different +labels on their system's board to use exactly the same BIOS, meaning that +the labels provided by the BIOS won't match the real ones. + +ECC memory +---------- + +As mentioned on the previous section, ECC memory has extra bits to be +used for error correction. So, on 64 bit systems, a memory module +has 64 bits of *data width*, and 74 bits of *total width*. So, there are +8 bits extra bits to be used for the error detection and correction +mechanisms. Those extra bits are called *syndrome*\ [#f1]_\ [#f2]_. + +So, when the cpu requests the memory controller to write a word with +*data width*, the memory controller calculates the *syndrome* in real time, +using Hamming code, or some other error correction code, like SECDED+, +producing a code with *total width* size. Such code is then written +on the memory modules. + +At read, the *total width* bits code is converted back, using the same +ECC code used on write, producing a word with *data width* and a *syndrome*. +The word with *data width* is sent to the CPU, even when errors happen. + +The memory controller also looks at the *syndrome* in order to check if +there was an error, and if the ECC code was able to fix such error. +If the error was corrected, a Corrected Error (CE) happened. If not, an +Uncorrected Error (UE) happened. + +The information about the CE/UE errors is stored on some special registers +at the memory controller and can be accessed by reading such registers, +either by BIOS, by some special CPUs or by Linux EDAC driver. On x86 64 +bit CPUs, such errors can also be retrieved via the Machine Check +Architecture (MCA)\ [#f3]_. + +.. [#f1] Please notice that several memory controllers allow operation on a + mode called "Lock-Step", where it groups two memory modules together, + doing 128-bit reads/writes. That gives 16 bits for error correction, with + significatively improves the error correction mechanism, at the expense + that, when an error happens, there's no way to know what memory module is + to blame. So, it has to blame both memory modules. + +.. [#f2] Some memory controllers also allow using memory in mirror mode. + On such mode, the same data is written to two memory modules. At read, + the system checks both memory modules, in order to check if both provide + identical data. On such configuration, when an error happens, there's no + way to know what memory module is to blame. So, it has to blame both + memory modules (or 4 memory modules, if the system is also on Lock-step + mode). + +.. [#f3] For more details about the Machine Check Architecture (MCA), + please read Documentation/x86/x86_64/machinecheck at the Kernel tree. + +EDAC - Error Detection And Correction +************************************* + +.. note:: + + "bluesmoke" was the name for this device driver subsystem when it + was "out-of-tree" and maintained at http://bluesmoke.sourceforge.net. + That site is mostly archaic now and can be used only for historical + purposes. + + When the subsystem was pushed upstream for the first time, on + Kernel 2.6.16, for the first time, it was renamed to ``EDAC``. + +Purpose +------- + +The ``edac`` kernel module's goal is to detect and report hardware errors +that occur within the computer system running under linux. + +Memory +------ + +Memory Correctable Errors (CE) and Uncorrectable Errors (UE) are the +primary errors being harvested. These types of errors are harvested by +the ``edac_mc`` device. + +Detecting CE events, then harvesting those events and reporting them, +**can** but must not necessarily be a predictor of future UE events. With +CE events only, the system can and will continue to operate as no data +has been damaged yet. + +However, preventive maintenance and proactive part replacement of memory +modules exhibiting CEs can reduce the likelihood of the dreaded UE events +and system panics. + +Other hardware elements +----------------------- + +A new feature for EDAC, the ``edac_device`` class of device, was added in +the 2.6.23 version of the kernel. + +This new device type allows for non-memory type of ECC hardware detectors +to have their states harvested and presented to userspace via the sysfs +interface. + +Some architectures have ECC detectors for L1, L2 and L3 caches, +along with DMA engines, fabric switches, main data path switches, +interconnections, and various other hardware data paths. If the hardware +reports it, then a edac_device device probably can be constructed to +harvest and present that to userspace. + + +PCI bus scanning +---------------- + +In addition, PCI devices are scanned for PCI Bus Parity and SERR Errors +in order to determine if errors are occurring during data transfers. + +The presence of PCI Parity errors must be examined with a grain of salt. +There are several add-in adapters that do **not** follow the PCI specification +with regards to Parity generation and reporting. The specification says +the vendor should tie the parity status bits to 0 if they do not intend +to generate parity. Some vendors do not do this, and thus the parity bit +can "float" giving false positives. + +There is a PCI device attribute located in sysfs that is checked by +the EDAC PCI scanning code. If that attribute is set, PCI parity/error +scanning is skipped for that device. The attribute is:: + + broken_parity_status + +and is located in ``/sys/devices/pci<XXX>/0000:XX:YY.Z`` directories for +PCI devices. + + +Versioning +---------- + +EDAC is composed of a "core" module (``edac_core.ko``) and several Memory +Controller (MC) driver modules. On a given system, the CORE is loaded +and one MC driver will be loaded. Both the CORE and the MC driver (or +``edac_device`` driver) have individual versions that reflect current +release level of their respective modules. + +Thus, to "report" on what version a system is running, one must report +both the CORE's and the MC driver's versions. + + +Loading +------- + +If ``edac`` was statically linked with the kernel then no loading +is necessary. If ``edac`` was built as modules then simply modprobe +the ``edac`` pieces that you need. You should be able to modprobe +hardware-specific modules and have the dependencies load the necessary +core modules. + +Example:: + + $ modprobe amd76x_edac + +loads both the ``amd76x_edac.ko`` memory controller module and the +``edac_mc.ko`` core module. + + +Sysfs interface +--------------- + +EDAC presents a ``sysfs`` interface for control and reporting purposes. It +lives in the /sys/devices/system/edac directory. + +Within this directory there currently reside 2 components: + + ======= ============================== + mc memory controller(s) system + pci PCI control and status system + ======= ============================== + + + +Memory Controller (mc) Model +---------------------------- + +Each ``mc`` device controls a set of memory modules [#f4]_. These modules +are laid out in a Chip-Select Row (``csrowX``) and Channel table (``chX``). +There can be multiple csrows and multiple channels. + +.. [#f4] Nowadays, the term DIMM (Dual In-line Memory Module) is widely + used to refer to a memory module, although there are other memory + packaging alternatives, like SO-DIMM, SIMM, etc. Along this document, + and inside the EDAC system, the term "dimm" is used for all memory + modules, even when they use a different kind of packaging. + +Memory controllers allow for several csrows, with 8 csrows being a +typical value. Yet, the actual number of csrows depends on the layout of +a given motherboard, memory controller and memory module characteristics. + +Dual channels allow for dual data length (e. g. 128 bits, on 64 bit systems) +data transfers to/from the CPU from/to memory. Some newer chipsets allow +for more than 2 channels, like Fully Buffered DIMMs (FB-DIMMs) memory +controllers. The following example will assume 2 channels: + + +------------+-----------------------+ + | Chip | Channels | + | Select +-----------+-----------+ + | rows | ``ch0`` | ``ch1`` | + +============+===========+===========+ + | ``csrow0`` | DIMM_A0 | DIMM_B0 | + +------------+ | | + | ``csrow1`` | | | + +------------+-----------+-----------+ + | ``csrow2`` | DIMM_A1 | DIMM_B1 | + +------------+ | | + | ``csrow3`` | | | + +------------+-----------+-----------+ + +In the above example, there are 4 physical slots on the motherboard +for memory DIMMs: + + +---------+---------+ + | DIMM_A0 | DIMM_B0 | + +---------+---------+ + | DIMM_A1 | DIMM_B1 | + +---------+---------+ + +Labels for these slots are usually silk-screened on the motherboard. +Slots labeled ``A`` are channel 0 in this example. Slots labeled ``B`` are +channel 1. Notice that there are two csrows possible on a physical DIMM. +These csrows are allocated their csrow assignment based on the slot into +which the memory DIMM is placed. Thus, when 1 DIMM is placed in each +Channel, the csrows cross both DIMMs. + +Memory DIMMs come single or dual "ranked". A rank is a populated csrow. +Thus, 2 single ranked DIMMs, placed in slots DIMM_A0 and DIMM_B0 above +will have just one csrow (csrow0). csrow1 will be empty. On the other +hand, when 2 dual ranked DIMMs are similarly placed, then both csrow0 +and csrow1 will be populated. The pattern repeats itself for csrow2 and +csrow3. + +The representation of the above is reflected in the directory +tree in EDAC's sysfs interface. Starting in directory +``/sys/devices/system/edac/mc``, each memory controller will be +represented by its own ``mcX`` directory, where ``X`` is the +index of the MC:: + + ..../edac/mc/ + | + |->mc0 + |->mc1 + |->mc2 + .... + +Under each ``mcX`` directory each ``csrowX`` is again represented by a +``csrowX``, where ``X`` is the csrow index:: + + .../mc/mc0/ + | + |->csrow0 + |->csrow2 + |->csrow3 + .... + +Notice that there is no csrow1, which indicates that csrow0 is composed +of a single ranked DIMMs. This should also apply in both Channels, in +order to have dual-channel mode be operational. Since both csrow2 and +csrow3 are populated, this indicates a dual ranked set of DIMMs for +channels 0 and 1. + +Within each of the ``mcX`` and ``csrowX`` directories are several EDAC +control and attribute files. + +``mcX`` directories +------------------- + +In ``mcX`` directories are EDAC control and attribute files for +this ``X`` instance of the memory controllers. + +For a description of the sysfs API, please see: + + Documentation/ABI/testing/sysfs-devices-edac + + +``dimmX`` or ``rankX`` directories +---------------------------------- + +The recommended way to use the EDAC subsystem is to look at the information +provided by the ``dimmX`` or ``rankX`` directories [#f5]_. + +A typical EDAC system has the following structure under +``/sys/devices/system/edac/``\ [#f6]_:: + + /sys/devices/system/edac/ + ├── mc + │ ├── mc0 + │ │ ├── ce_count + │ │ ├── ce_noinfo_count + │ │ ├── dimm0 + │ │ │ ├── dimm_dev_type + │ │ │ ├── dimm_edac_mode + │ │ │ ├── dimm_label + │ │ │ ├── dimm_location + │ │ │ ├── dimm_mem_type + │ │ │ ├── size + │ │ │ └── uevent + │ │ ├── max_location + │ │ ├── mc_name + │ │ ├── reset_counters + │ │ ├── seconds_since_reset + │ │ ├── size_mb + │ │ ├── ue_count + │ │ ├── ue_noinfo_count + │ │ └── uevent + │ ├── mc1 + │ │ ├── ce_count + │ │ ├── ce_noinfo_count + │ │ ├── dimm0 + │ │ │ ├── dimm_dev_type + │ │ │ ├── dimm_edac_mode + │ │ │ ├── dimm_label + │ │ │ ├── dimm_location + │ │ │ ├── dimm_mem_type + │ │ │ ├── size + │ │ │ └── uevent + │ │ ├── max_location + │ │ ├── mc_name + │ │ ├── reset_counters + │ │ ├── seconds_since_reset + │ │ ├── size_mb + │ │ ├── ue_count + │ │ ├── ue_noinfo_count + │ │ └── uevent + │ └── uevent + └── uevent + +In the ``dimmX`` directories are EDAC control and attribute files for +this ``X`` memory module: + +- ``size`` - Total memory managed by this csrow attribute file + + This attribute file displays, in count of megabytes, the memory + that this csrow contains. + +- ``dimm_dev_type`` - Device type attribute file + + This attribute file will display what type of DRAM device is + being utilized on this DIMM. + Examples: + + - x1 + - x2 + - x4 + - x8 + +- ``dimm_edac_mode`` - EDAC Mode of operation attribute file + + This attribute file will display what type of Error detection + and correction is being utilized. + +- ``dimm_label`` - memory module label control file + + This control file allows this DIMM to have a label assigned + to it. With this label in the module, when errors occur + the output can provide the DIMM label in the system log. + This becomes vital for panic events to isolate the + cause of the UE event. + + DIMM Labels must be assigned after booting, with information + that correctly identifies the physical slot with its + silk screen label. This information is currently very + motherboard specific and determination of this information + must occur in userland at this time. + +- ``dimm_location`` - location of the memory module + + The location can have up to 3 levels, and describe how the + memory controller identifies the location of a memory module. + Depending on the type of memory and memory controller, it + can be: + + - *csrow* and *channel* - used when the memory controller + doesn't identify a single DIMM - e. g. in ``rankX`` dir; + - *branch*, *channel*, *slot* - typically used on FB-DIMM memory + controllers; + - *channel*, *slot* - used on Nehalem and newer Intel drivers. + +- ``dimm_mem_type`` - Memory Type attribute file + + This attribute file will display what type of memory is currently + on this csrow. Normally, either buffered or unbuffered memory. + Examples: + + - Registered-DDR + - Unbuffered-DDR + +.. [#f5] On some systems, the memory controller doesn't have any logic + to identify the memory module. On such systems, the directory is called ``rankX`` and works on a similar way as the ``csrowX`` directories. + On modern Intel memory controllers, the memory controller identifies the + memory modules directly. On such systems, the directory is called ``dimmX``. + +.. [#f6] There are also some ``power`` directories and ``subsystem`` + symlinks inside the sysfs mapping that are automatically created by + the sysfs subsystem. Currently, they serve no purpose. + +``csrowX`` directories +---------------------- + +When CONFIG_EDAC_LEGACY_SYSFS is enabled, sysfs will contain the ``csrowX`` +directories. As this API doesn't work properly for Rambus, FB-DIMMs and +modern Intel Memory Controllers, this is being deprecated in favor of +``dimmX`` directories. + +In the ``csrowX`` directories are EDAC control and attribute files for +this ``X`` instance of csrow: + + +- ``ue_count`` - Total Uncorrectable Errors count attribute file + + This attribute file displays the total count of uncorrectable + errors that have occurred on this csrow. If panic_on_ue is set + this counter will not have a chance to increment, since EDAC + will panic the system. + + +- ``ce_count`` - Total Correctable Errors count attribute file + + This attribute file displays the total count of correctable + errors that have occurred on this csrow. This count is very + important to examine. CEs provide early indications that a + DIMM is beginning to fail. This count field should be + monitored for non-zero values and report such information + to the system administrator. + + +- ``size_mb`` - Total memory managed by this csrow attribute file + + This attribute file displays, in count of megabytes, the memory + that this csrow contains. + + +- ``mem_type`` - Memory Type attribute file + + This attribute file will display what type of memory is currently + on this csrow. Normally, either buffered or unbuffered memory. + Examples: + + - Registered-DDR + - Unbuffered-DDR + + +- ``edac_mode`` - EDAC Mode of operation attribute file + + This attribute file will display what type of Error detection + and correction is being utilized. + + +- ``dev_type`` - Device type attribute file + + This attribute file will display what type of DRAM device is + being utilized on this DIMM. + Examples: + + - x1 + - x2 + - x4 + - x8 + + +- ``ch0_ce_count`` - Channel 0 CE Count attribute file + + This attribute file will display the count of CEs on this + DIMM located in channel 0. + + +- ``ch0_ue_count`` - Channel 0 UE Count attribute file + + This attribute file will display the count of UEs on this + DIMM located in channel 0. + + +- ``ch0_dimm_label`` - Channel 0 DIMM Label control file + + + This control file allows this DIMM to have a label assigned + to it. With this label in the module, when errors occur + the output can provide the DIMM label in the system log. + This becomes vital for panic events to isolate the + cause of the UE event. + + DIMM Labels must be assigned after booting, with information + that correctly identifies the physical slot with its + silk screen label. This information is currently very + motherboard specific and determination of this information + must occur in userland at this time. + + +- ``ch1_ce_count`` - Channel 1 CE Count attribute file + + + This attribute file will display the count of CEs on this + DIMM located in channel 1. + + +- ``ch1_ue_count`` - Channel 1 UE Count attribute file + + + This attribute file will display the count of UEs on this + DIMM located in channel 0. + + +- ``ch1_dimm_label`` - Channel 1 DIMM Label control file + + This control file allows this DIMM to have a label assigned + to it. With this label in the module, when errors occur + the output can provide the DIMM label in the system log. + This becomes vital for panic events to isolate the + cause of the UE event. + + DIMM Labels must be assigned after booting, with information + that correctly identifies the physical slot with its + silk screen label. This information is currently very + motherboard specific and determination of this information + must occur in userland at this time. + + +System Logging +-------------- + +If logging for UEs and CEs is enabled, then system logs will contain +information indicating that errors have been detected:: + + EDAC MC0: CE page 0x283, offset 0xce0, grain 8, syndrome 0x6ec3, row 0, channel 1 "DIMM_B1": amd76x_edac + EDAC MC0: CE page 0x1e5, offset 0xfb0, grain 8, syndrome 0xb741, row 0, channel 1 "DIMM_B1": amd76x_edac + + +The structure of the message is: + + +---------------------------------------+-------------+ + | Content + Example | + +=======================================+=============+ + | The memory controller | MC0 | + +---------------------------------------+-------------+ + | Error type | CE | + +---------------------------------------+-------------+ + | Memory page | 0x283 | + +---------------------------------------+-------------+ + | Offset in the page | 0xce0 | + +---------------------------------------+-------------+ + | The byte granularity | grain 8 | + | or resolution of the error | | + +---------------------------------------+-------------+ + | The error syndrome | 0xb741 | + +---------------------------------------+-------------+ + | Memory row | row 0 + + +---------------------------------------+-------------+ + | Memory channel | channel 1 | + +---------------------------------------+-------------+ + | DIMM label, if set prior | DIMM B1 | + +---------------------------------------+-------------+ + | And then an optional, driver-specific | | + | message that may have additional | | + | information. | | + +---------------------------------------+-------------+ + +Both UEs and CEs with no info will lack all but memory controller, error +type, a notice of "no info" and then an optional, driver-specific error +message. + + +PCI Bus Parity Detection +------------------------ + +On Header Type 00 devices, the primary status is looked at for any +parity error regardless of whether parity is enabled on the device or +not. (The spec indicates parity is generated in some cases). On Header +Type 01 bridges, the secondary status register is also looked at to see +if parity occurred on the bus on the other side of the bridge. + + +Sysfs configuration +------------------- + +Under ``/sys/devices/system/edac/pci`` are control and attribute files as +follows: + + +- ``check_pci_parity`` - Enable/Disable PCI Parity checking control file + + This control file enables or disables the PCI Bus Parity scanning + operation. Writing a 1 to this file enables the scanning. Writing + a 0 to this file disables the scanning. + + Enable:: + + echo "1" >/sys/devices/system/edac/pci/check_pci_parity + + Disable:: + + echo "0" >/sys/devices/system/edac/pci/check_pci_parity + + +- ``pci_parity_count`` - Parity Count + + This attribute file will display the number of parity errors that + have been detected. + + +Module parameters +----------------- + +- ``edac_mc_panic_on_ue`` - Panic on UE control file + + An uncorrectable error will cause a machine panic. This is usually + desirable. It is a bad idea to continue when an uncorrectable error + occurs - it is indeterminate what was uncorrected and the operating + system context might be so mangled that continuing will lead to further + corruption. If the kernel has MCE configured, then EDAC will never + notice the UE. + + LOAD TIME:: + + module/kernel parameter: edac_mc_panic_on_ue=[0|1] + + RUN TIME:: + + echo "1" > /sys/module/edac_core/parameters/edac_mc_panic_on_ue + + +- ``edac_mc_log_ue`` - Log UE control file + + + Generate kernel messages describing uncorrectable errors. These errors + are reported through the system message log system. UE statistics + will be accumulated even when UE logging is disabled. + + LOAD TIME:: + + module/kernel parameter: edac_mc_log_ue=[0|1] + + RUN TIME:: + + echo "1" > /sys/module/edac_core/parameters/edac_mc_log_ue + + +- ``edac_mc_log_ce`` - Log CE control file + + + Generate kernel messages describing correctable errors. These + errors are reported through the system message log system. + CE statistics will be accumulated even when CE logging is disabled. + + LOAD TIME:: + + module/kernel parameter: edac_mc_log_ce=[0|1] + + RUN TIME:: + + echo "1" > /sys/module/edac_core/parameters/edac_mc_log_ce + + +- ``edac_mc_poll_msec`` - Polling period control file + + + The time period, in milliseconds, for polling for error information. + Too small a value wastes resources. Too large a value might delay + necessary handling of errors and might loose valuable information for + locating the error. 1000 milliseconds (once each second) is the current + default. Systems which require all the bandwidth they can get, may + increase this. + + LOAD TIME:: + + module/kernel parameter: edac_mc_poll_msec=[0|1] + + RUN TIME:: + + echo "1000" > /sys/module/edac_core/parameters/edac_mc_poll_msec + + +- ``panic_on_pci_parity`` - Panic on PCI PARITY Error + + + This control file enables or disables panicking when a parity + error has been detected. + + + module/kernel parameter:: + + edac_panic_on_pci_pe=[0|1] + + Enable:: + + echo "1" > /sys/module/edac_core/parameters/edac_panic_on_pci_pe + + Disable:: + + echo "0" > /sys/module/edac_core/parameters/edac_panic_on_pci_pe + + + +EDAC device type +---------------- + +In the header file, edac_pci.h, there is a series of edac_device structures +and APIs for the EDAC_DEVICE. + +User space access to an edac_device is through the sysfs interface. + +At the location ``/sys/devices/system/edac`` (sysfs) new edac_device devices +will appear. + +There is a three level tree beneath the above ``edac`` directory. For example, +the ``test_device_edac`` device (found at the http://bluesmoke.sourceforget.net +website) installs itself as:: + + /sys/devices/system/edac/test-instance + +in this directory are various controls, a symlink and one or more ``instance`` +directories. + +The standard default controls are: + + ============== ======================================================= + log_ce boolean to log CE events + log_ue boolean to log UE events + panic_on_ue boolean to ``panic`` the system if an UE is encountered + (default off, can be set true via startup script) + poll_msec time period between POLL cycles for events + ============== ======================================================= + +The test_device_edac device adds at least one of its own custom control: + + ============== ================================================== + test_bits which in the current test driver does nothing but + show how it is installed. A ported driver can + add one or more such controls and/or attributes + for specific uses. + One out-of-tree driver uses controls here to allow + for ERROR INJECTION operations to hardware + injection registers + ============== ================================================== + +The symlink points to the 'struct dev' that is registered for this edac_device. + +Instances +--------- + +One or more instance directories are present. For the ``test_device_edac`` +case: + + +----------------+ + | test-instance0 | + +----------------+ + + +In this directory there are two default counter attributes, which are totals of +counter in deeper subdirectories. + + ============== ==================================== + ce_count total of CE events of subdirectories + ue_count total of UE events of subdirectories + ============== ==================================== + +Blocks +------ + +At the lowest directory level is the ``block`` directory. There can be 0, 1 +or more blocks specified in each instance: + + +-------------+ + | test-block0 | + +-------------+ + +In this directory the default attributes are: + + ============== ================================================ + ce_count which is counter of CE events for this ``block`` + of hardware being monitored + ue_count which is counter of UE events for this ``block`` + of hardware being monitored + ============== ================================================ + + +The ``test_device_edac`` device adds 4 attributes and 1 control: + + ================== ==================================================== + test-block-bits-0 for every POLL cycle this counter + is incremented + test-block-bits-1 every 10 cycles, this counter is bumped once, + and test-block-bits-0 is set to 0 + test-block-bits-2 every 100 cycles, this counter is bumped once, + and test-block-bits-1 is set to 0 + test-block-bits-3 every 1000 cycles, this counter is bumped once, + and test-block-bits-2 is set to 0 + ================== ==================================================== + + + ================== ==================================================== + reset-counters writing ANY thing to this control will + reset all the above counters. + ================== ==================================================== + + +Use of the ``test_device_edac`` driver should enable any others to create their own +unique drivers for their hardware systems. + +The ``test_device_edac`` sample driver is located at the +http://bluesmoke.sourceforge.net project site for EDAC. + + +Usage of EDAC APIs on Nehalem and newer Intel CPUs +-------------------------------------------------- + +On older Intel architectures, the memory controller was part of the North +Bridge chipset. Nehalem, Sandy Bridge, Ivy Bridge, Haswell, Sky Lake and +newer Intel architectures integrated an enhanced version of the memory +controller (MC) inside the CPUs. + +This chapter will cover the differences of the enhanced memory controllers +found on newer Intel CPUs, such as ``i7core_edac``, ``sb_edac`` and +``sbx_edac`` drivers. + +.. note:: + + The Xeon E7 processor families use a separate chip for the memory + controller, called Intel Scalable Memory Buffer. This section doesn't + apply for such families. + +1) There is one Memory Controller per Quick Patch Interconnect + (QPI). At the driver, the term "socket" means one QPI. This is + associated with a physical CPU socket. + + Each MC have 3 physical read channels, 3 physical write channels and + 3 logic channels. The driver currently sees it as just 3 channels. + Each channel can have up to 3 DIMMs. + + The minimum known unity is DIMMs. There are no information about csrows. + As EDAC API maps the minimum unity is csrows, the driver sequentially + maps channel/DIMM into different csrows. + + For example, supposing the following layout:: + + Ch0 phy rd0, wr0 (0x063f4031): 2 ranks, UDIMMs + dimm 0 1024 Mb offset: 0, bank: 8, rank: 1, row: 0x4000, col: 0x400 + dimm 1 1024 Mb offset: 4, bank: 8, rank: 1, row: 0x4000, col: 0x400 + Ch1 phy rd1, wr1 (0x063f4031): 2 ranks, UDIMMs + dimm 0 1024 Mb offset: 0, bank: 8, rank: 1, row: 0x4000, col: 0x400 + Ch2 phy rd3, wr3 (0x063f4031): 2 ranks, UDIMMs + dimm 0 1024 Mb offset: 0, bank: 8, rank: 1, row: 0x4000, col: 0x400 + + The driver will map it as:: + + csrow0: channel 0, dimm0 + csrow1: channel 0, dimm1 + csrow2: channel 1, dimm0 + csrow3: channel 2, dimm0 + + exports one DIMM per csrow. + + Each QPI is exported as a different memory controller. + +2) The MC has the ability to inject errors to test drivers. The drivers + implement this functionality via some error injection nodes: + + For injecting a memory error, there are some sysfs nodes, under + ``/sys/devices/system/edac/mc/mc?/``: + + - ``inject_addrmatch/*``: + Controls the error injection mask register. It is possible to specify + several characteristics of the address to match an error code:: + + dimm = the affected dimm. Numbers are relative to a channel; + rank = the memory rank; + channel = the channel that will generate an error; + bank = the affected bank; + page = the page address; + column (or col) = the address column. + + each of the above values can be set to "any" to match any valid value. + + At driver init, all values are set to any. + + For example, to generate an error at rank 1 of dimm 2, for any channel, + any bank, any page, any column:: + + echo 2 >/sys/devices/system/edac/mc/mc0/inject_addrmatch/dimm + echo 1 >/sys/devices/system/edac/mc/mc0/inject_addrmatch/rank + + To return to the default behaviour of matching any, you can do:: + + echo any >/sys/devices/system/edac/mc/mc0/inject_addrmatch/dimm + echo any >/sys/devices/system/edac/mc/mc0/inject_addrmatch/rank + + - ``inject_eccmask``: + specifies what bits will have troubles, + + - ``inject_section``: + specifies what ECC cache section will get the error:: + + 3 for both + 2 for the highest + 1 for the lowest + + - ``inject_type``: + specifies the type of error, being a combination of the following bits:: + + bit 0 - repeat + bit 1 - ecc + bit 2 - parity + + - ``inject_enable``: + starts the error generation when something different than 0 is written. + + All inject vars can be read. root permission is needed for write. + + Datasheet states that the error will only be generated after a write on an + address that matches inject_addrmatch. It seems, however, that reading will + also produce an error. + + For example, the following code will generate an error for any write access + at socket 0, on any DIMM/address on channel 2:: + + echo 2 >/sys/devices/system/edac/mc/mc0/inject_addrmatch/channel + echo 2 >/sys/devices/system/edac/mc/mc0/inject_type + echo 64 >/sys/devices/system/edac/mc/mc0/inject_eccmask + echo 3 >/sys/devices/system/edac/mc/mc0/inject_section + echo 1 >/sys/devices/system/edac/mc/mc0/inject_enable + dd if=/dev/mem of=/dev/null seek=16k bs=4k count=1 >& /dev/null + + For socket 1, it is needed to replace "mc0" by "mc1" at the above + commands. + + The generated error message will look like:: + + EDAC MC0: UE row 0, channel-a= 0 channel-b= 0 labels "-": NON_FATAL (addr = 0x0075b980, socket=0, Dimm=0, Channel=2, syndrome=0x00000040, count=1, Err=8c0000400001009f:4000080482 (read error: read ECC error)) + +3) Corrected Error memory register counters + + Those newer MCs have some registers to count memory errors. The driver + uses those registers to report Corrected Errors on devices with Registered + DIMMs. + + However, those counters don't work with Unregistered DIMM. As the chipset + offers some counters that also work with UDIMMs (but with a worse level of + granularity than the default ones), the driver exposes those registers for + UDIMM memories. + + They can be read by looking at the contents of ``all_channel_counts/``:: + + $ for i in /sys/devices/system/edac/mc/mc0/all_channel_counts/*; do echo $i; cat $i; done + /sys/devices/system/edac/mc/mc0/all_channel_counts/udimm0 + 0 + /sys/devices/system/edac/mc/mc0/all_channel_counts/udimm1 + 0 + /sys/devices/system/edac/mc/mc0/all_channel_counts/udimm2 + 0 + + What happens here is that errors on different csrows, but at the same + dimm number will increment the same counter. + So, in this memory mapping:: + + csrow0: channel 0, dimm0 + csrow1: channel 0, dimm1 + csrow2: channel 1, dimm0 + csrow3: channel 2, dimm0 + + The hardware will increment udimm0 for an error at the first dimm at either + csrow0, csrow2 or csrow3; + + The hardware will increment udimm1 for an error at the second dimm at either + csrow0, csrow2 or csrow3; + + The hardware will increment udimm2 for an error at the third dimm at either + csrow0, csrow2 or csrow3; + +4) Standard error counters + + The standard error counters are generated when an mcelog error is received + by the driver. Since, with UDIMM, this is counted by software, it is + possible that some errors could be lost. With RDIMM's, they display the + contents of the registers + +Reference documents used on ``amd64_edac`` +------------------------------------------ + +``amd64_edac`` module is based on the following documents +(available from http://support.amd.com/en-us/search/tech-docs): + +1. :Title: BIOS and Kernel Developer's Guide for AMD Athlon 64 and AMD + Opteron Processors + :AMD publication #: 26094 + :Revision: 3.26 + :Link: http://support.amd.com/TechDocs/26094.PDF + +2. :Title: BIOS and Kernel Developer's Guide for AMD NPT Family 0Fh + Processors + :AMD publication #: 32559 + :Revision: 3.00 + :Issue Date: May 2006 + :Link: http://support.amd.com/TechDocs/32559.pdf + +3. :Title: BIOS and Kernel Developer's Guide (BKDG) For AMD Family 10h + Processors + :AMD publication #: 31116 + :Revision: 3.00 + :Issue Date: September 07, 2007 + :Link: http://support.amd.com/TechDocs/31116.pdf + +4. :Title: BIOS and Kernel Developer's Guide (BKDG) for AMD Family 15h + Models 30h-3Fh Processors + :AMD publication #: 49125 + :Revision: 3.06 + :Issue Date: 2/12/2015 (latest release) + :Link: http://support.amd.com/TechDocs/49125_15h_Models_30h-3Fh_BKDG.pdf + +5. :Title: BIOS and Kernel Developer's Guide (BKDG) for AMD Family 15h + Models 60h-6Fh Processors + :AMD publication #: 50742 + :Revision: 3.01 + :Issue Date: 7/23/2015 (latest release) + :Link: http://support.amd.com/TechDocs/50742_15h_Models_60h-6Fh_BKDG.pdf + +6. :Title: BIOS and Kernel Developer's Guide (BKDG) for AMD Family 16h + Models 00h-0Fh Processors + :AMD publication #: 48751 + :Revision: 3.03 + :Issue Date: 2/23/2015 (latest release) + :Link: http://support.amd.com/TechDocs/48751_16h_bkdg.pdf + +Credits +======= + +* Written by Doug Thompson <dougthompson@xmission.com> + + - 7 Dec 2005 + - 17 Jul 2007 Updated + +* |copy| Mauro Carvalho Chehab + + - 05 Aug 2009 Nehalem interface + - 26 Oct 2016 Converted to ReST and cleanups at the Nehalem section + +* EDAC authors/maintainers: + + - Doug Thompson, Dave Jiang, Dave Peterson et al, + - Mauro Carvalho Chehab + - Borislav Petkov + - original author: Thayne Harbaugh |