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Message-Id: <1931444790.41750165203442.JavaMail.epsvc@epcpadp1new>
Date: Tue, 17 Jun 2025 18:09:24 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: dan.j.williams@...el.com, dave@...olabs.net,
jonathan.cameron@...wei.com, dave.jiang@...el.com,
alison.schofield@...el.com, vishal.l.verma@...el.com, ira.weiny@...el.com
Cc: a.manzanares@...sung.com, nifan.cxl@...il.com, anisa.su@...sung.com,
vishak.g@...sung.com, krish.reddy@...sung.com, arun.george@...sung.com,
alok.rathore@...sung.com, s.neeraj@...sung.com, neeraj.kernel@...il.com,
linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
nvdimm@...ts.linux.dev, gost.dev@...sung.com, cpgs@...sung.com
Subject: [RFC PATCH 00/20] Add CXL LSA 2.1 format support in nvdimm and cxl
pmem
Introduction:
=============
CXL Persistent Memory (Pmem) devices region, namespace and content must be
persistent across system reboot. In order to achieve this persistency, it
uses Label Storage Area (LSA) to store respective metadata. During system
reboot, stored metadata in LSA is used to bring back the region, namespace
and content of CXL device in its previous state.
CXL specification provides Get_LSA (4102h) and Set_LSA (4103h) mailbox
commands to access the LSA area. nvdimm driver is using same commands to
get/set LSA data.
There are three types of LSA format and these are part of following
specifications:
- v1.1: https://pmem.io/documents/NVDIMM_Namespace_Spec.pdf
- v1.2: https://uefi.org/sites/default/files/resources/UEFI_Spec_2_7.pdf
- v2.1: https://computeexpresslink.org/wp-content/uploads/2024/02/CXL-2.0-Specification.pdf
Basic differences between these LSA formats:
- v1.1: Support Namespace persistency. Size of Namespace Label is 128 bytes
- v1.2: Support Namespace persistency. Size of Namespace Label is 256 bytes
- v2.1: Support Namespace and Region persistency. Size of Namespace and
Region Label is 256 bytes.
Linux nvdimm driver supports only v1.1 and v1.2 LSA format. CXL pmem device
require support of LSA v2.1 format for region and namespace persistency.
Initial support of LSA 2.1 was add in [1].
This patchset adds support of LSA 2.1 in nvdimm and cxl pmem driver.
Patch 1: Introduce NDD_CXL_LABEL flag and Update cxl label index as per v2.1
Patch 2-4: Update namespace label as per v2.1
Patch 5-12: Introduce cxl region labels and modify existing change accordingly
Patch 13: Refactor cxl pmem region auto assembly
Patch 14-18: Save cxl region info in LSA and region recreation during reboot
Patch 19: Segregate out cxl pmem region code from region.c to pmem_region.c
Patch 20: Introduce cxl region addition/deletion attributes
Testing:
========
In order to test this patchset, I also added the support of LSA v2.1 format
in ndctl. ndctl changes are available at [2]. After review, I’ll push in
ndctl repo for community review.
1. Used Qemu using following CXL topology
M2="-object memory-backend-file,id=cxl-mem1,share=on,mem-path=$TMP_DIR/cxltest.raw,size=512M \
-object memory-backend-file,id=cxl-lsa1,share=on,mem-path=$TMP_DIR/lsa.raw,size=1M \
-object memory-backend-file,id=cxl-mem2,share=on,mem-path=$TMP_DIR/cxltest2.raw,size=512M \
-object memory-backend-file,id=cxl-lsa2,share=on,mem-path=$TMP_DIR/lsa2.raw,size=1M \
-device pxb-cxl,bus_nr=10,bus=pcie.0,id=cxl.1 \
-device cxl-rp,port=1,bus=cxl.1,id=root_port11,chassis=0,slot=1 \
-device cxl-type3,bus=root_port11,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem1,sn=1 \
-device cxl-rp,port=2,bus=cxl.1,id=root_port12,chassis=0,slot=2 \
-device cxl-type3,bus=root_port12,memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem2,sn=2 \
-M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=8k"
2. Create cxl region on both devices
cxl create-region -d decoder0.0 -m mem0
cxl create-region -d decoder0.0 -m mem1
root@...UCXL6060pmem:~# cxl list
[
{
"memdevs":[
{
"memdev":"mem0",
"pmem_size":536870912,
"serial":2,
"host":"0000:0c:00.0",
"firmware_version":"BWFW VERSION 00"
},
{
"memdev":"mem1",
"pmem_size":536870912,
"serial":1,
"host":"0000:0b:00.0",
"firmware_version":"BWFW VERSION 00"
}
]
},
{
"regions":[
{
"region":"region0",
"resource":45365592064,
"size":536870912,
"type":"pmem",
"interleave_ways":1,
"interleave_granularity":256,
"decode_state":"commit",
"qos_class_mismatch":true
},
{
"region":"region1",
"resource":45902462976,
"size":536870912,
"type":"pmem",
"interleave_ways":1,
"interleave_granularity":256,
"decode_state":"commit",
"qos_class_mismatch":true
}
]
}
]
3. Re-Start Qemu and we could see cxl region persistency using "cxl list"
4. Create namespace for both regions
root@...UCXL6060pmem:~# ndctl create-namespace --mode=fsdax --region=region0 --size=128M
{
"dev":"namespace0.0",
"mode":"fsdax",
"map":"dev",
"size":"124.00 MiB (130.02 MB)",
"uuid":"3f6dcdc5-d289-4b0c-ad16-82636c82bec1",
"sector_size":512,
"align":2097152,
"blockdev":"pmem0"
}
root@...UCXL6060pmem:~# ndctl create-namespace --mode=fsdax --region=region1 --size=256M
{
"dev":"namespace1.0",
"mode":"fsdax",
"map":"dev",
"size":"250.00 MiB (262.14 MB)",
"uuid":"6b9083c9-cb1a-447b-894d-fdfd2f3dbed2",
"sector_size":512,
"align":2097152,
"blockdev":"pmem1"
}
root@...UCXL6060pmem:~# time ndctl create-namespace --mode=fsdax --region=region0 --size=256M
{
"dev":"namespace0.1",
"mode":"fsdax",
"map":"dev",
"size":"250.00 MiB (262.14 MB)",
"uuid":"c2071802-8c24-4f9c-a6c1-f6bb6589e561",
"sector_size":512,
"align":2097152,
"blockdev":"pmem0.1"
}
real 0m47.517s
user 0m0.209s
sys 0m26.879s
root@...UCXL6060pmem:~# time ndctl create-namespace --mode=fsdax --region=region1 --size=128M
{
"dev":"namespace1.1",
"mode":"fsdax",
"map":"dev",
"size":"124.00 MiB (130.02 MB)",
"uuid":"13bc8de3-53d3-4c3d-b252-be7efefe80ee",
"sector_size":512,
"align":2097152,
"blockdev":"pmem1.1"
}
real 0m33.459s
user 0m0.243s
sys 0m13.590s
root@...UCXL6060pmem:~# ndctl list
[
{
"dev":"namespace1.0",
"mode":"fsdax",
"map":"dev",
"size":262144000,
"uuid":"6b9083c9-cb1a-447b-894d-fdfd2f3dbed2",
"sector_size":512,
"align":2097152,
"blockdev":"pmem1"
},
{
"dev":"namespace1.1",
"mode":"fsdax",
"map":"dev",
"size":130023424,
"uuid":"13bc8de3-53d3-4c3d-b252-be7efefe80ee",
"sector_size":512,
"align":2097152,
"blockdev":"pmem1.1"
},
{
"dev":"namespace0.1",
"mode":"fsdax",
"map":"dev",
"size":262144000,
"uuid":"c2071802-8c24-4f9c-a6c1-f6bb6589e561",
"sector_size":512,
"align":2097152,
"blockdev":"pmem0.1"
},
{
"dev":"namespace0.0",
"mode":"fsdax",
"map":"dev",
"size":130023424,
"uuid":"3f6dcdc5-d289-4b0c-ad16-82636c82bec1",
"sector_size":512,
"align":2097152,
"blockdev":"pmem0"
}
]
5. Re-Start Qemu and we could see
- Region persistency using "cxl list"
- Namespace persistency using "ndctl list" and cat /proc/iomem
root@...UCXL6060pmem:~# cat /proc/iomem
a90000000-b8fffffff : CXL Window 0
a90000000-aafffffff : Persistent Memory
a90000000-aafffffff : region0
a90000000-a97ffffff : namespace0.0
a98000000-aa7ffffff : namespace0.1
ab0000000-acfffffff : Persistent Memory
ab0000000-acfffffff : region1
ab0000000-abfffffff : namespace1.0
ac0000000-ac7ffffff : namespace1.1
- NOTE: We can see some lag in restart, Its WIP
6. Also verify LSA version using "ndctl read-labels -j nmem0 -u"
root@...UCXL6060pmem:~# ndctl read-labels -j nmem0
{
"dev":"nmem0",
"index":[
{
"signature":"NAMESPACE_INDEX",
"major":2,
"minor":1,
"labelsize":256,
"seq":2,
"nslot":4090
},
{
"signature":"NAMESPACE_INDEX",
"major":2,
"minor":1,
"labelsize":256,
"seq":1,
"nslot":4090
}
],
"label":[
{
"type":"68bb2c0a-5a77-4937-9f85-3caf41a0f93c",
"uuid":"9a26b9ce-a859-4a63-b1b7-fd176105770d",
"name":"",
"flags":8,
"nrange":1,
"position":0,
"dpa":134217728,
"rawsize":268435456,
"slot":0,
"align":0,
"region_uuid":"de512bdc-9731-4e5f-838c-be2e9b94ea72",
"abstraction_uuid":"266400ba-fb9f-4677-bcb0-968f11d0d225",
"lbasize":512
},
{
"type":"529d7c61-da07-47c4-a93f-ecdf2c06f444",
"uuid":"de512bdc-9731-4e5f-838c-be2e9b94ea72",
"flags":0,
"nlabel":1,
"position":0,
"dpa":0,
"rawsize":536870912,
"hpa":45365592064,
"slot":1,
"interleave granularity":256,
"align":0
},
{
"type":"68bb2c0a-5a77-4937-9f85-3caf41a0f93c",
"uuid":"a90d211a-b28d-48c7-bfe7-99560d3825ef",
"name":"",
"flags":0,
"nrange":1,
"position":0,
"dpa":0,
"rawsize":134217728,
"slot":2,
"align":0,
"region_uuid":"de512bdc-9731-4e5f-838c-be2e9b94ea72",
"abstraction_uuid":"266400ba-fb9f-4677-bcb0-968f11d0d225",
"lbasize":512
},
{
"type":"68bb2c0a-5a77-4937-9f85-3caf41a0f93c",
"uuid":"9a26b9ce-a859-4a63-b1b7-fd176105770d",
"name":"",
"flags":0,
"nrange":1,
"position":0,
"dpa":134217728,
"rawsize":268435456,
"slot":3,
"align":0,
"region_uuid":"de512bdc-9731-4e5f-838c-be2e9b94ea72",
"abstraction_uuid":"266400ba-fb9f-4677-bcb0-968f11d0d225",
"lbasize":512
}
]
}
read 1 nmem
- NOTE: We have following UUID types as per CXL Spec
"type":"529d7c61-da07-47c4-a93f-ecdf2c06f444" is region label
"type":"68bb2c0a-5a77-4937-9f85-3caf41a0f93c" is namespace label
Limitation (WIP):
================
Current changes only support interleave way == 1
Observation:
============
First time namespace creation using ndctl takes around 10 to 20 second time
while executing "devm_memremap_pages" at [3]
As using this patchset, after auto region creation, namespace creation is
happening in boot sequence (if nvdimm and cxl drivers are static), It is
therefore boot sequence is increased by around 10 to 20 sec.
[1]: https://lore.kernel.org/all/163116432405.2460985.5547867384570123403.stgit@dwillia2-desk3.amr.corp.intel.com/
[2]: https://github.com/neerajoss/ndctl/tree/linux-cxl/CXL_LSA_2.1_Support
[3]: https://elixir.bootlin.com/linux/v6.13.7/source/drivers/nvdimm/pmem.c#L520
Neeraj Kumar (20):
nvdimm/label: Introduce NDD_CXL_LABEL flag to set cxl label format
nvdimm/label: Prep patch to accommodate cxl lsa 2.1 support
nvdimm/namespace_label: Add namespace label changes as per CXL LSAv2.1
nvdimm/label: CXL labels skip the need for 'interleave-set cookie'
nvdimm/region_label: Add region label updation routine
nvdimm/region_label: Add region label deletion routine
nvdimm/namespace_label: Update namespace init_labels and its region_uuid
nvdimm/label: Include region label in slot validation
nvdimm/namespace_label: Skip region label during ns label DPA reservation
nvdimm/region_label: Preserve cxl region information from region label
nvdimm/region_label: Export routine to fetch region information
nvdimm/namespace_label: Skip region label during namespace creation
cxl/mem: Refactor cxl pmem region auto-assembling
cxl/region: Add cxl pmem region creation routine for region persistency
cxl: Add a routine to find cxl root decoder on cxl bus
cxl/mem: Preserve cxl root decoder during mem probe
cxl/pmem: Preserve region information into nd_set
cxl/pmem: Add support of cxl lsa 2.1 support in cxl pmem
cxl/pmem_region: Prep patch to accommodate pmem_region attributes
cxl/pmem_region: Add cxl region label updation and deletion device attributes
drivers/cxl/Kconfig | 12 +
drivers/cxl/core/Makefile | 1 +
drivers/cxl/core/core.h | 8 +-
drivers/cxl/core/pmem_region.c | 325 ++++++++++++++++++++++++++
drivers/cxl/core/port.c | 72 +++++-
drivers/cxl/core/region.c | 383 +++++++++++++++---------------
drivers/cxl/cxl.h | 46 +++-
drivers/cxl/cxlmem.h | 1 +
drivers/cxl/mem.c | 27 ++-
drivers/cxl/pmem.c | 72 +++++-
drivers/cxl/port.c | 38 ---
drivers/nvdimm/dimm.c | 5 +
drivers/nvdimm/dimm_devs.c | 28 +++
drivers/nvdimm/label.c | 403 ++++++++++++++++++++++++++++----
drivers/nvdimm/label.h | 20 +-
drivers/nvdimm/namespace_devs.c | 149 ++++++++----
drivers/nvdimm/nd-core.h | 2 +
drivers/nvdimm/nd.h | 81 ++++++-
drivers/nvdimm/region_devs.c | 5 +
include/linux/libnvdimm.h | 28 +++
tools/testing/cxl/Kbuild | 1 +
21 files changed, 1364 insertions(+), 343 deletions(-)
create mode 100644 drivers/cxl/core/pmem_region.c
base-commit: 448a60e85ae2afe2cb760f5d2ed2c8a49d2bd1b4
--
2.34.1
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