Skip to content

Commit f90b738

Browse files
shijujose4bp3tk0v
shijujose4
authored and
bp3tk0v
committed
EDAC: Add scrub control feature
Add a scrub control to manage memory scrubbers in the system. Devices with a scrub feature register with the EDAC device driver which retrieves the scrub descriptor from the scrub driver and exposes the control attributes for a instance to userspace at /sys/bus/edac/devices/<dev-name>/scrubX/. The common sysfs scrub control interface abstracts the control of arbitrary scrubbing functionality into a common set of functions. The attribute nodes are only present if the client driver has implemented the corresponding attribute callback function and passed the operations to the device driver during registration. [ bp: Massage commit message, docs and code, simplify text a bit. Integrate fixup for: https://lore.kernel.org/r/202502251009.0sGkolEJ-lkp@intel.com Reported-by: kernel test robot <lkp@intel.com> Reported-by: Dan Carpenter <dan.carpenter@linaro.org> ] Co-developed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Shiju Jose <shiju.jose@huawei.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Tested-by: Daniel Ferguson <danielf@os.amperecomputing.com> Tested-by: Fan Ni <fan.ni@samsung.com> Link: https://lore.kernel.org/r/20250212143654.1893-3-shiju.jose@huawei.com
1 parent db99ea5 commit f90b738

File tree

9 files changed

+638
-4
lines changed

9 files changed

+638
-4
lines changed

‎Documentation/ABI/testing/sysfs-edac-scrub

Lines changed: 69 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,69 @@
1+
What: /sys/bus/edac/devices/<dev-name>/scrubX
2+
Date: March 2025
3+
KernelVersion: 6.15
4+
Contact: linux-edac@vger.kernel.org
5+
Description:
6+
The sysfs EDAC bus devices /<dev-name>/scrubX subdirectory
7+
belongs to an instance of memory scrub control feature,
8+
where <dev-name> directory corresponds to a device/memory
9+
region registered with the EDAC device driver for the
10+
scrub control feature.
11+
12+
The sysfs scrub attr nodes are only present if the parent
13+
driver has implemented the corresponding attr callback
14+
function and provided the necessary operations to the EDAC
15+
device driver during registration.
16+
17+
What: /sys/bus/edac/devices/<dev-name>/scrubX/addr
18+
Date: March 2025
19+
KernelVersion: 6.15
20+
Contact: linux-edac@vger.kernel.org
21+
Description:
22+
(RW) The base address of the memory region to be scrubbed
23+
for on-demand scrubbing. Setting address starts scrubbing.
24+
The size must be set before that.
25+
26+
The readback addr value is non-zero if the requested
27+
on-demand scrubbing is in progress, zero otherwise.
28+
29+
What: /sys/bus/edac/devices/<dev-name>/scrubX/size
30+
Date: March 2025
31+
KernelVersion: 6.15
32+
Contact: linux-edac@vger.kernel.org
33+
Description:
34+
(RW) The size of the memory region to be scrubbed
35+
(on-demand scrubbing).
36+
37+
What: /sys/bus/edac/devices/<dev-name>/scrubX/enable_background
38+
Date: March 2025
39+
KernelVersion: 6.15
40+
Contact: linux-edac@vger.kernel.org
41+
Description:
42+
(RW) Start/Stop background (patrol) scrubbing if supported.
43+
44+
What: /sys/bus/edac/devices/<dev-name>/scrubX/min_cycle_duration
45+
Date: March 2025
46+
KernelVersion: 6.15
47+
Contact: linux-edac@vger.kernel.org
48+
Description:
49+
(RO) Supported minimum scrub cycle duration in seconds
50+
by the memory scrubber.
51+
52+
What: /sys/bus/edac/devices/<dev-name>/scrubX/max_cycle_duration
53+
Date: March 2025
54+
KernelVersion: 6.15
55+
Contact: linux-edac@vger.kernel.org
56+
Description:
57+
(RO) Supported maximum scrub cycle duration in seconds
58+
by the memory scrubber.
59+
60+
What: /sys/bus/edac/devices/<dev-name>/scrubX/current_cycle_duration
61+
Date: March 2025
62+
KernelVersion: 6.15
63+
Contact: linux-edac@vger.kernel.org
64+
Description:
65+
(RW) The current scrub cycle duration in seconds and must be
66+
within the supported range by the memory scrubber.
67+
68+
Scrub has an overhead when running and that may want to be
69+
reduced by taking longer to do it.

‎Documentation/edac/features.rst

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -91,3 +91,9 @@ High level design is illustrated in the following diagram::
9191
3. RAS dynamic feature controller - Userspace sample modules in rasdaemon for
9292
dynamic scrub/repair control to issue scrubbing/repair when excess number
9393
of corrected memory errors are reported in a short span of time.
94+
95+
RAS features
96+
------------
97+
1. Memory Scrub
98+
99+
Memory scrub features are documented in `Documentation/edac/scrub.rst`.

‎Documentation/edac/index.rst

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -8,3 +8,4 @@ EDAC Subsystem
88
:maxdepth: 1
99

1010
features
11+
scrub

‎Documentation/edac/scrub.rst

Lines changed: 264 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,264 @@
1+
.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.2-no-invariants-or-later
2+
3+
=============
4+
Scrub Control
5+
=============
6+
7+
Copyright (c) 2024-2025 HiSilicon Limited.
8+
9+
:Author: Shiju Jose <shiju.jose@huawei.com>
10+
:License: The GNU Free Documentation License, Version 1.2 without
11+
Invariant Sections, Front-Cover Texts nor Back-Cover Texts.
12+
(dual licensed under the GPL v2)
13+
14+
- Written for: 6.15
15+
16+
Introduction
17+
------------
18+
19+
Increasing DRAM size and cost have made memory subsystem reliability an
20+
important concern. These modules are used where potentially corrupted data
21+
could cause expensive or fatal issues. Memory errors are among the top
22+
hardware failures that cause server and workload crashes.
23+
24+
Memory scrubbing is a feature where an ECC (Error-Correcting Code) engine
25+
reads data from each memory media location, corrects if necessary and writes
26+
the corrected data back to the same memory media location.
27+
28+
DIMMs can be scrubbed at a configurable rate to detect uncorrected memory
29+
errors and attempt recovery from detected errors, providing the following
30+
benefits:
31+
32+
1. Proactively scrubbing DIMMs reduces the chance of a correctable error
33+
becoming uncorrectable.
34+
35+
2. When detected, uncorrected errors caught in unallocated memory pages are
36+
isolated and prevented from being allocated to an application or the OS.
37+
38+
3. This reduces the likelihood of software or hardware products encountering
39+
memory errors.
40+
41+
4. The additional data on failures in memory may be used to build up
42+
statistics that are later used to decide whether to use memory repair
43+
technologies such as Post Package Repair or Sparing.
44+
45+
There are 2 types of memory scrubbing:
46+
47+
1. Background (patrol) scrubbing while the DRAM is otherwise idle.
48+
49+
2. On-demand scrubbing for a specific address range or region of memory.
50+
51+
Several types of interfaces to hardware memory scrubbers have been
52+
identified, such as CXL memory device patrol scrub, CXL DDR5 ECS, ACPI
53+
RAS2 memory scrubbing, and ACPI NVDIMM ARS (Address Range Scrub).
54+
55+
The control mechanisms vary across different memory scrubbers. To enable
56+
standardized userspace tooling, there is a need to present these controls
57+
through a standardized ABI.
58+
59+
A generic memory EDAC scrub control allows users to manage underlying
60+
scrubbers in the system through a standardized sysfs control interface. It
61+
abstracts the management of various scrubbing functionalities into a unified
62+
set of functions.
63+
64+
Use cases of common scrub control feature
65+
-----------------------------------------
66+
67+
1. Several types of interfaces for hardware memory scrubbers have been
68+
identified, including the CXL memory device patrol scrub, CXL DDR5 ECS,
69+
ACPI RAS2 memory scrubbing features, ACPI NVDIMM ARS (Address Range Scrub),
70+
and software-based memory scrubbers.
71+
72+
Of the identified interfaces to hardware memory scrubbers some support
73+
control over patrol (background) scrubbing (e.g., ACPI RAS2, CXL) and/or
74+
on-demand scrubbing (e.g., ACPI RAS2, ACPI ARS). However, the scrub control
75+
interfaces vary between memory scrubbers, highlighting the need for
76+
a standardized, generic sysfs scrub control interface that is accessible to
77+
userspace for administration and use by scripts/tools.
78+
79+
2. User-space scrub controls allow users to disable scrubbing if necessary,
80+
for example, to disable background patrol scrubbing or adjust the scrub
81+
rate for performance-aware operations where background activities need to
82+
be minimized or disabled.
83+
84+
3. User-space tools enable on-demand scrubbing for specific address ranges,
85+
provided that the scrubber supports this functionality.
86+
87+
4. User-space tools can also control memory DIMM scrubbing at a configurable
88+
scrub rate via sysfs scrub controls. This approach offers several benefits:
89+
90+
4.1. Detects uncorrectable memory errors early, before user access to affected
91+
memory, helping facilitate recovery.
92+
93+
4.2. Reduces the likelihood of correctable errors developing into uncorrectable
94+
errors.
95+
96+
5. Policy control for hotplugged memory is necessary because there may not
97+
be a system-wide BIOS or similar control to manage scrub settings for a CXL
98+
device added after boot. Determining these settings is a policy decision,
99+
balancing reliability against performance, so userspace should control it.
100+
Therefore, a unified interface is recommended for handling this function in
101+
a way that aligns with other similar interfaces, rather than creating a
102+
separate one.
103+
104+
Scrubbing features
105+
------------------
106+
107+
CXL Memory Scrubbing features
108+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
109+
110+
CXL spec r3.1 [1]_ section 8.2.9.9.11.1 describes the memory device patrol
111+
scrub control feature. The device patrol scrub proactively locates and makes
112+
corrections to errors in regular cycle. The patrol scrub control allows the
113+
userspace request to change CXL patrol scrubber's configurations.
114+
115+
The patrol scrub control allows the requester to specify the number of
116+
hours in which the patrol scrub cycles must be completed, provided that
117+
the requested scrub rate must be within the supported range of the
118+
scrub rate that the device is capable of. In the CXL driver, the
119+
number of seconds per scrub cycles, which user requests via sysfs, is
120+
rescaled to hours per scrub cycles.
121+
122+
In addition, they allow the host to disable the feature in case it interferes
123+
with performance-aware operations which require the background operations to
124+
be turned off.
125+
126+
Error Check Scrub (ECS)
127+
~~~~~~~~~~~~~~~~~~~~~~~
128+
129+
CXL spec r3.1 [1]_ section 8.2.9.9.11.2 describes Error Check Scrub (ECS)
130+
- a feature defined in the JEDEC DDR5 SDRAM Specification (JESD79-5) and
131+
allowing DRAM to internally read, correct single-bit errors, and write back
132+
corrected data bits to the DRAM array while providing transparency to error
133+
counts.
134+
135+
The DDR5 device contains number of memory media Field Replaceable Units (FRU)
136+
per device. The DDR5 ECS feature and thus the ECS control driver supports
137+
configuring the ECS parameters per FRU.
138+
139+
ACPI RAS2 Hardware-based Memory Scrubbing
140+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
141+
142+
ACPI spec 6.5 [2]_ section 5.2.21 ACPI RAS2 describes an ACPI RAS2 table
143+
which provides interfaces for platform RAS features and supports independent
144+
RAS controls and capabilities for a given RAS feature for multiple instances
145+
of the same component in a given system.
146+
147+
Memory RAS features apply to RAS capabilities, controls and operations that
148+
are specific to memory. RAS2 PCC sub-spaces for memory-specific RAS features
149+
have a Feature Type of 0x00 (Memory).
150+
151+
The platform can use the hardware-based memory scrubbing feature to expose
152+
controls and capabilities associated with hardware-based memory scrub
153+
engines. The RAS2 memory scrubbing feature supports as per spec,
154+
155+
1. Independent memory scrubbing controls for each NUMA domain, identified
156+
using its proximity domain.
157+
158+
2. Provision for background (patrol) scrubbing of the entire memory system,
159+
as well as on-demand scrubbing for a specific region of memory.
160+
161+
ACPI Address Range Scrubbing (ARS)
162+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
163+
164+
ACPI spec 6.5 [2]_ section 9.19.7.2 describes Address Range Scrubbing (ARS).
165+
ARS allows the platform to communicate memory errors to system software.
166+
This capability allows system software to prevent accesses to addresses with
167+
uncorrectable errors in memory. ARS functions manage all NVDIMMs present in
168+
the system. Only one scrub can be in progress system wide at any given time.
169+
170+
The following functions are supported as per the specification:
171+
172+
1. Query ARS Capabilities for a given address range, indicates platform
173+
supports the ACPI NVDIMM Root Device Unconsumed Error Notification.
174+
175+
2. Start ARS triggers an Address Range Scrub for the given memory range.
176+
Address scrubbing can be done for volatile or persistent memory, or both.
177+
178+
3. Query ARS Status command allows software to get the status of ARS,
179+
including the progress of ARS and ARS error record.
180+
181+
4. Clear Uncorrectable Error.
182+
183+
5. Translate SPA
184+
185+
6. ARS Error Inject etc.
186+
187+
The kernel supports an existing control for ARS and ARS is currently not
188+
supported in EDAC.
189+
190+
.. [1] https://computeexpresslink.org/cxl-specification/
191+
192+
.. [2] https://uefi.org/specs/ACPI/6.5/
193+
194+
Comparison of various scrubbing features
195+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
196+
197+
+--------------+-----------+-----------+-----------+-----------+
198+
| | ACPI | CXL patrol| CXL ECS | ARS |
199+
| Name | RAS2 | scrub | | |
200+
+--------------+-----------+-----------+-----------+-----------+
201+
| | | | | |
202+
| On-demand | Supported | No | No | Supported |
203+
| Scrubbing | | | | |
204+
| | | | | |
205+
+--------------+-----------+-----------+-----------+-----------+
206+
| | | | | |
207+
| Background | Supported | Supported | Supported | No |
208+
| scrubbing | | | | |
209+
| | | | | |
210+
+--------------+-----------+-----------+-----------+-----------+
211+
| | | | | |
212+
| Mode of | Scrub ctrl| per device| per memory| Unknown |
213+
| scrubbing | per NUMA | | media | |
214+
| | domain. | | | |
215+
+--------------+-----------+-----------+-----------+-----------+
216+
| | | | | |
217+
| Query scrub | Supported | Supported | Supported | Supported |
218+
| capabilities | | | | |
219+
| | | | | |
220+
+--------------+-----------+-----------+-----------+-----------+
221+
| | | | | |
222+
| Setting | Supported | No | No | Supported |
223+
| address range| | | | |
224+
| | | | | |
225+
+--------------+-----------+-----------+-----------+-----------+
226+
| | | | | |
227+
| Setting | Supported | Supported | No | No |
228+
| scrub rate | | | | |
229+
| | | | | |
230+
+--------------+-----------+-----------+-----------+-----------+
231+
| | | | | |
232+
| Unit for | Not | in hours | No | No |
233+
| scrub rate | Defined | | | |
234+
| | | | | |
235+
+--------------+-----------+-----------+-----------+-----------+
236+
| | Supported | | | |
237+
| Scrub | on-demand | No | No | Supported |
238+
| status/ | scrubbing | | | |
239+
| Completion | only | | | |
240+
+--------------+-----------+-----------+-----------+-----------+
241+
| UC error | |CXL general|CXL general| ACPI UCE |
242+
| reporting | Exception |media/DRAM |media/DRAM | notify and|
243+
| | |event/media|event/media| query |
244+
| | |scan? |scan? | ARS status|
245+
+--------------+-----------+-----------+-----------+-----------+
246+
| | | | | |
247+
| Support for | Supported | Supported | Supported | No |
248+
| EDAC control | | | | |
249+
| | | | | |
250+
+--------------+-----------+-----------+-----------+-----------+
251+
252+
The File System
253+
---------------
254+
255+
The control attributes of a registered scrubber instance could be
256+
accessed in:
257+
258+
/sys/bus/edac/devices/<dev-name>/scrubX/
259+
260+
sysfs
261+
-----
262+
263+
Sysfs files are documented in
264+
`Documentation/ABI/testing/sysfs-edac-scrub`

‎drivers/edac/Kconfig

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -75,6 +75,15 @@ config EDAC_GHES
7575

7676
In doubt, say 'Y'.
7777

78+
config EDAC_SCRUB
79+
bool "EDAC scrub feature"
80+
help
81+
The EDAC scrub feature is optional and is designed to control the
82+
memory scrubbers in the system. The common sysfs scrub interface
83+
abstracts the control of various arbitrary scrubbing functionalities
84+
into a unified set of functions.
85+
Say 'y/n' to enable/disable EDAC scrub feature.
86+
7887
config EDAC_AMD64
7988
tristate "AMD64 (Opteron, Athlon64)"
8089
depends on AMD_NB && EDAC_DECODE_MCE

‎drivers/edac/Makefile

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@ edac_core-y := edac_mc.o edac_device.o edac_mc_sysfs.o
1212
edac_core-y += edac_module.o edac_device_sysfs.o wq.o
1313

1414
edac_core-$(CONFIG_EDAC_DEBUG) += debugfs.o
15+
edac_core-$(CONFIG_EDAC_SCRUB) += scrub.o
1516

1617
ifdef CONFIG_PCI
1718
edac_core-y += edac_pci.o edac_pci_sysfs.o

0 commit comments

Comments
 (0)