Re: [PATCH V6 00/18] Add CXL LSA 2.1 format support in nvdimm and cxl pmem

Dave Jiang
2026-01-23T17:52:33Z

On 1/23/26 4:30 AM, Neeraj Kumar wrote:
> 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.

Hi Neeraj,
I'm attempting to vet the series before applying to cxl/next. But it seems to be failing multiple unit regression tests in cxl_test. We need to figure out why before the series can be merged. Most likely the changes in this series also require cxl_test updates. Can you please take a look? I will also take a look and try to help you address the issues. Thanks

Ok: 10
Expected Fail: 0
Fail: 4
Unexpected Pass: 0
Skipped: 1
Timeout: 0

The script below [1] can get you up and running with a qemu environment where you can run cxl_test.

.../run_qemu/run_qemu.sh --cxl --cxl-test --cxl-debug --hmat -r wipe

cd ndctl
meson test -C build --suite=cxl

[1] https://github.com/pmem/run_qemu

DJ

>
> 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: Skip the need for 'interleave-set cookie' for LSA 2.1 support
> Patch 3-9: Introduce region label and update namespace label as per LSA 2.1
> Patch 10: Refactor cxl pmem region auto assembly using Dan's Infra
> Patch 11-13: Save cxl region info in LSA and region recreation during reboot
> Patch 14:15: Segregate out cxl pmem region code from region.c to pmem_region.c
> Patch 16: Introduce cxl region addition/deletion attributes
> Patch 17-18: Add support of cxl pmem region re-creation from CXL as per LSA 2.1
>
> 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-mem11,share=on,mem-path=$TMP_DIR/cxltest11.raw,size=4G \
> -object memory-backend-file,id=cxl-lsa11,share=on,mem-path=$TMP_DIR/lsa.raw11,size=1M \
> -object memory-backend-file,id=cxl-mem21,share=on,mem-path=$TMP_DIR/cxltest21.raw,size=4G \
> -object memory-backend-file,id=cxl-lsa21,share=on,mem-path=$TMP_DIR/lsa21.raw,size=1M \
> -device pxb-cxl,bus=pcie.0,bus_nr=10,id=cxl.1 \
> -device cxl-rp,port=110,bus=cxl.1,id=root_port11,chassis=0,slot=11 \
> -device cxl-type3,bus=root_port11,memdev=cxl-mem11,lsa=cxl-lsa11,id=cxl-pmem11,sn=11 \
> -device pxb-cxl,bus=pcie.0,bus_nr=20,id=cxl.2 \
> -device cxl-rp,port=210,bus=cxl.2,id=root_port21,chassis=0,slot=21 \
> -device cxl-type3,bus=root_port21,memdev=cxl-mem21,lsa=cxl-lsa21,id=cxl-pmem21,sn=21 \
> -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=8G,cxl-fmw.0.interleave-granularity=8k,cxl-fmw.1.targets.0=cxl.2,cxl-fmw.1.size=8G"
>
> 2. Create cxl region on both devices
> cxl create-region -d decoder0.1 -m mem0
> cxl create-region -d decoder0.0 -m mem1
>
> root@QEMUCXL6060pmem:~# cxl list
> [
> {
> "memdevs":[
> {
> "memdev":"mem0",
> "pmem_size":4294967296,
> "serial":21,
> "host":"0000:15:00.0",
> "firmware_version":"BWFW VERSION 00"
> },
> {
> "memdev":"mem1",
> "pmem_size":4294967296,
> "serial":11,
> "host":"0000:0b:00.0",
> "firmware_version":"BWFW VERSION 00"
> }
> ]
> },
> {
> "regions":[
> {
> "region":"region0",
> "resource":45365592064,
> "size":4294967296,
> "type":"pmem",
> "interleave_ways":1,
> "interleave_granularity":256,
> "decode_state":"commit",
> "qos_class_mismatch":true
> },
> {
> "region":"region1",
> "resource":53955526656,
> "size":4294967296,
> "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@QEMUCXL6060pmem:~# 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":"5f9e28b4-f403-4e72-bb06-307ead53dec4",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem0.1"
> }
>
> real 1m8.795s
> user 0m0.098s
> sys 0m48.699s
>
>
> root@QEMUCXL6060pmem:~# 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":"33682096-7364-412d-bfbc-fa7568939abd",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem1.1"
> }
>
>
> root@QEMUCXL6060pmem:~# time ndctl create-namespace --mode=fsdax --region=region0 --size=128M
> {
> "dev":"namespace0.0",
> "mode":"fsdax",
> "map":"dev",
> "size":"124.00 MiB (130.02 MB)",
> "uuid":"9681af0e-349a-401e-9833-1cf8903d58fa",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem0"
> }
>
> real 0m39.805s
> user 0m0.138s
> sys 0m21.485s
>
>
> root@QEMUCXL6060pmem:~# time ndctl create-namespace --mode=fsdax --region=region1 --size=256M
> {
> "dev":"namespace1.0",
> "mode":"fsdax",
> "map":"dev",
> "size":"250.00 MiB (262.14 MB)",
> "uuid":"15f1c8d5-416f-4d2e-9e39-d17ce8f73a42",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem1"
> }
>
> real 0m43.899s
> user 0m0.113s
> sys 0m31.167s
>
>
> root@QEMUCXL6060pmem:~# time ndctl create-namespace --mode=fsdax --region=region0 --size=128M
> {
> "dev":"namespace0.0",
> "mode":"fsdax",
> "map":"dev",
> "size":"124.00 MiB (130.02 MB)",
> "uuid":"9681af0e-349a-401e-9833-1cf8903d58fa",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem0"
> }
>
> real 0m39.805s
> user 0m0.138s
> sys 0m21.485s
>
>
> root@QEMUCXL6060pmem:~# ndctl list
> [
> {
> "dev":"namespace1.0",
> "mode":"fsdax",
> "map":"dev",
> "size":262144000,
> "uuid":"15f1c8d5-416f-4d2e-9e39-d17ce8f73a42",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem1"
> },
> {
> "dev":"namespace1.1",
> "mode":"fsdax",
> "map":"dev",
> "size":130023424,
> "uuid":"33682096-7364-412d-bfbc-fa7568939abd",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem1.1"
> },
> {
> "dev":"namespace0.1",
> "mode":"fsdax",
> "map":"dev",
> "size":262144000,
> "uuid":"5f9e28b4-f403-4e72-bb06-307ead53dec4",
> "sector_size":512,
> "align":2097152,
> "blockdev":"pmem0.1"
> },
> {
> "dev":"namespace0.0",
> "mode":"fsdax",
> "map":"dev",
> "size":130023424,
> "uuid":"9681af0e-349a-401e-9833-1cf8903d58fa",
> "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@QEMUCXL6060pmem:~# cat /proc/iomem
> fed1c000-fed1ffff : Reserved
> feffc000-feffffff : Reserved
> fffc0000-ffffffff : Reserved
> 100000000-27fffffff : System RAM
> a90000000-c8fffffff : CXL Window 0
> a90000000-b8fffffff : Persistent Memory
> a90000000-b8fffffff : region0
> a90000000-a97ffffff : namespace0.0
> a98000000-aa7ffffff : namespace0.1
> c90000000-e8fffffff : CXL Window 1
> c90000000-d8fffffff : Persistent Memory
> c90000000-d8fffffff : region1
> c90000000-c9fffffff : namespace1.0
> ca0000000-ca7ffffff : namespace1.1
> 380000000000-38000000ffff : PCI Bus 0000:0a
> 380000000000-38000000ffff : 0000:0a:00.0
>
> - NOTE: We can see some lag in restart. Look at Observesation below
>
> 6. Also verify LSA version using "ndctl read-labels -j nmem0"
> root@QEMUCXL6060pmem:~# time 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":"5b33b940-6767-4951-b923-952455482f52",
> "name":"",
> "flags":8,
> "nrange":1,
> "position":0,
> "dpa":134217728,
> "rawsize":268435456,
> "slot":0,
> "align":0,
> "region_uuid":"a1482e6b-968e-4297-b2f5-bf1733966e55",
> "abstraction_uuid":"266400ba-fb9f-4677-bcb0-968f11d0d225",
> "lbasize":512
> },
> {
> "type":"529d7c61-da07-47c4-a93f-ecdf2c06f444",
> "uuid":"a1482e6b-968e-4297-b2f5-bf1733966e55",
> "flags":0,
> "nlabel":1,
> "position":0,
> "dpa":0,
> "rawsize":4294967296,
> "hpa":45365592064,
> "slot":1,
> "interleave granularity":256,
> "align":0
> },
> {
> "type":"68bb2c0a-5a77-4937-9f85-3caf41a0f93c",
> "uuid":"2c1c33c0-909b-4c6a-8de4-dfc6c13ae82c",
> "name":"",
> "flags":0,
> "nrange":1,
> "position":0,
> "dpa":0,
> "rawsize":134217728,
> "slot":2,
> "align":0,
> "region_uuid":"a1482e6b-968e-4297-b2f5-bf1733966e55",
> "abstraction_uuid":"266400ba-fb9f-4677-bcb0-968f11d0d225",
> "lbasize":512
> },
> {
> "type":"68bb2c0a-5a77-4937-9f85-3caf41a0f93c",
> "uuid":"5b33b940-6767-4951-b923-952455482f52",
> "name":"",
> "flags":0,
> "nrange":1,
> "position":0,
> "dpa":134217728,
> "rawsize":268435456,
> "slot":3,
> "align":0,
> "region_uuid":"a1482e6b-968e-4297-b2f5-bf1733966e55",
> "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.
>
> Changes
> =======
> Changes in v5->v6
> -----------------
> - Find v5 link at [4]
> - Find v4 link at [5]
> - Find v3 link at [6]
> - Find v2 link at [7]
> - v1 patch-set was broken. Find the v1 links at [8] and [9]
>
> [Misc]
> - Rebase with for-7.0/cxl-init
>
> [PATCH 01/18]
> - Add Ira RB tag
>
> [PATCH 03/18]
> - Use export_uuid() instead of uuid_copy() [Jonathan]
> - Add Jonathan RB tag
> - Add Ira RB tag
>
> [PATCH 04/18]
> - Move the assignments at relevant place [Jonathan]
> - Rename lslot to label_slot [Jonathan]
> - Add Ira RB tag
>
> [PATCH 05/18]
> - Add Jonathan RB tag
> - Add Ira RB tag
>
> [PATCH 06/18]
> - Add Jonathan RB tag
> - Add Ira RB tag
>
> [PATCH 07/18]
> - Add Ira RB tag
>
> [PATCH 08/18]
> - use export_uuid() to avoid casts to uuid_t * [Jonathan]
> - Add Jonathan RB tag
> - Add Ira RB tag
>
> [PATCH 09/18]
> - Add Jonathan RB tag
> - Add Ira RB tag
>
> [PATCH 10/18]
> - Initialize struct cxl_memdev_attach variable [Jonathan]
> - Add Jonathan RB tag
>
> [PATCH 10/18]
> - Its a new patch addition in this series
> - Seperate out renaming of __create_region() to cxl_create_region() [Jonathan]
>
> [PATCH 11/18]
> - Remove usage of cxl_dpa_free() from alloc_region_dpa() [Jonathan]
>
> [PATCH 13/18]
> - Add Jonathan RB tag
>
> [PATCH 15/18]
> - Add Jonathan RB tag
>
> [PATCH 16/18]
> - Fix wrong name state with region_label_state [Jonathan]
> - Add Jonathan RB tag
>
> [PATCH 17/18]
> - Optimize loop matching [Jonathan]
> - Use reverse xmas tree stype [Jonathan]
>
> [PATCH 18/18]
> - Add Jonathan RB tag
>
>
> [1]: https://lore.kernel.org/all/163116432405.2460985.5547867384570123403.stgit@dwillia2-desk3.amr.corp.intel.com/
> [2]: https://github.com/neerajoss/ndctl/commits/linux-cxl/V1_CXL_LSA_2.1_Support/
> [3]: https://elixir.bootlin.com/linux/v6.13.7/source/drivers/nvdimm/pmem.c#L520
> [4]: https://lore.kernel.org/linux-cxl/20260109124437.4025893-1-s.neeraj@samsung.com/
> [5]: https://lore.kernel.org/linux-cxl/20250917134116.1623730-1-s.neeraj@samsung.com/
> [6]: https://lore.kernel.org/linux-cxl/20251119075255.2637388-1-s.neeraj@samsung.com/
> [7]: https://lore.kernel.org/linux-cxl/20250730121209.303202-1-s.neeraj@samsung.com/
> [8] v1 Cover Letter: https://lore.kernel.org/linux-cxl/1931444790.41750165203442.JavaMail.epsvc@epcpadp1new/
> [9] v1 Rest Thread: https://lore.kernel.org/linux-cxl/158453976.61750165203630.JavaMail.epsvc@epcpadp1new/
>
>
> Neeraj Kumar (18):
> nvdimm/label: Introduce NDD_REGION_LABELING flag to set region label
> nvdimm/label: CXL labels skip the need for 'interleave-set cookie'
> nvdimm/label: Add namespace/region label support as per LSA 2.1
> nvdimm/label: Include region label in slot validation
> nvdimm/label: Skip region label during ns label DPA reservation
> nvdimm/label: Preserve region label during namespace creation
> nvdimm/label: Add region label delete support
> nvdimm/label: Preserve cxl region information from region label
> nvdimm/label: Export routine to fetch region information
> cxl/mem: Refactor cxl pmem region auto-assembling
> cxl/region: Rename __create_region() to cxl_create_region()
> cxl/region: Add devm_cxl_pmem_add_region() for pmem region creation
> cxl/pmem: Preserve region information into nd_set
> cxl/pmem_region: Prep patch to accommodate pmem_region attributes
> cxl/pmem_region: Introduce CONFIG_CXL_PMEM_REGION for core/pmem_region.c
> cxl/pmem_region: Add sysfs attribute cxl region label updation/deletion
> cxl/pmem_region: Create pmem region using information parsed from LSA
> cxl/pmem: Add CXL LSA 2.1 support in cxl pmem
>
> Documentation/ABI/testing/sysfs-bus-cxl | 22 +
> drivers/cxl/Kconfig | 15 +
> drivers/cxl/core/Makefile | 1 +
> drivers/cxl/core/core.h | 35 +-
> drivers/cxl/core/pmem_region.c | 422 +++++++++++++++++
> drivers/cxl/core/region.c | 377 ++++++++-------
> drivers/cxl/cxl.h | 41 +-
> drivers/cxl/mem.c | 18 +-
> drivers/cxl/pci.c | 4 +-
> drivers/cxl/pmem.c | 15 +-
> drivers/cxl/port.c | 39 +-
> drivers/nvdimm/dimm.c | 5 +
> drivers/nvdimm/dimm_devs.c | 19 +
> drivers/nvdimm/label.c | 580 ++++++++++++++++++++----
> drivers/nvdimm/label.h | 18 +-
> drivers/nvdimm/namespace_devs.c | 82 +++-
> drivers/nvdimm/nd-core.h | 2 +
> drivers/nvdimm/nd.h | 64 +++
> drivers/nvdimm/region_devs.c | 10 +
> include/linux/libnvdimm.h | 28 ++
> tools/testing/cxl/Kbuild | 1 +
> 21 files changed, 1424 insertions(+), 374 deletions(-)
> create mode 100644 drivers/cxl/core/pmem_region.c
>
>
> base-commit: bc62f5b308cbdedf29132fe96e9d591e526527e1