7 Dec 2005
17 Jul 2007 Updated
+(c) Mauro Carvalho Chehab <mchehab@redhat.com>
+05 Aug 2009 Nehalem interface
EDAC is maintained and written by:
The 'test_device_edac' sample driver is located at the
bluesmoke.sourceforge.net project site for EDAC.
+=======================================================================
+NEHALEM USAGE OF EDAC APIs
+
+This chapter documents some EXPERIMENTAL mappings for EDAC API to handle
+Nehalem EDAC driver. They will likely be changed on future versions
+of the driver.
+
+Due to the way Nehalem exports Memory Controller data, some adjustments
+were done at i7core_edac driver. This chapter will cover those differences
+
+1) On Nehalem, there are 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 currenty 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 sequencially
+ maps channel/dimm into different csrows.
+
+ For example, suposing 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) Nehalem MC has the hability to generate errors. The driver implements 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) Nehalem specific Corrected Error memory counters
+
+ Nehalem 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 Dimms. 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 displays the
+ contents of the registers
projects / linux-flexiantxendom0-3.2.10.git / blobdiff