Re: [PATCH V6 10/18] cxl/mem: Refactor cxl pmem region auto-assembling

Dave Jiang
2026-01-27T23:45:32Z

On 1/26/26 3:48 PM, Dave Jiang wrote:
>
>
> On 1/23/26 4:31 AM, Neeraj Kumar wrote:
>> In 84ec985944ef3, devm_cxl_add_nvdimm() sequence was changed and called
>> before devm_cxl_add_endpoint(). It's because cxl pmem region auto-assembly
>> used to get called at last in cxl_endpoint_port_probe(), which requires
>> cxl_nvd presence.
>>
>> For cxl region persistency, region creation happens during nvdimm_probe
>> which need the completion of endpoint probe.
>>
>> In order to accommodate both cxl pmem region auto-assembly and cxl region
>> persistency, refactored following
>>
>> 1. Re-Sequence devm_cxl_add_nvdimm() after devm_cxl_add_endpoint(). This
>> will be called only after successful completion of endpoint probe.
>>
>> 2. Create cxl_region_discovery() which performs pmem region
>> auto-assembly and remove cxl pmem region auto-assembly from
>> cxl_endpoint_port_probe()
>>
>> 3. Register cxl_region_discovery() with devm_cxl_add_memdev() which gets
>> called during cxl_pci_probe() in context of cxl_mem_probe()
>>
>> 4. As cxlmd->attach->probe() calls registered cxl_region_discovery(), so
>> move devm_cxl_add_nvdimm() before cxlmd->attach->probe(). It guarantees
>> both the completion of endpoint probe and cxl_nvd presence before
>> calling cxlmd->attach->probe().
>>
>> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>> Signed-off-by: Neeraj Kumar <s.neeraj@samsung.com>
>
> Hi Neeraj,
> Just FYI this is the patch that breaks the auto-region assemble in cxl_test.

So it's missing this part in cxl_test. cxl_test auto region is now showing up. But now I'm hitting some lockdep issues.

---
diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
index cb87e8c0e63c..03af15edd988 100644
--- a/tools/testing/cxl/test/mem.c
+++ b/tools/testing/cxl/test/mem.c
@@ -1686,6 +1686,7 @@ static void cxl_mock_test_feat_init(struct cxl_mockmem_data *mdata)

static int cxl_mock_mem_probe(struct platform_device *pdev)
{
+ struct cxl_memdev_attach memdev_attach = { 0 };
struct device *dev = &pdev->dev;
struct cxl_memdev *cxlmd;
struct cxl_memdev_state *mds;
@@ -1767,7 +1768,8 @@ static int cxl_mock_mem_probe(struct platform_device *pdev)

cxl_mock_add_event_logs(&mdata->mes);

- cxlmd = devm_cxl_add_memdev(cxlds, NULL);
+ memdev_attach.probe = cxl_region_discovery;
+ cxlmd = devm_cxl_add_memdev(cxlds, &memdev_attach);
if (IS_ERR(cxlmd))
return PTR_ERR(cxlmd);

---

>
> DJ
>
>> ---
>> drivers/cxl/core/region.c | 37 +++++++++++++++++++++++++++++++++++++
>> drivers/cxl/cxl.h | 5 +++++
>> drivers/cxl/mem.c | 18 +++++++++---------
>> drivers/cxl/pci.c | 4 +++-
>> drivers/cxl/port.c | 39 +--------------------------------------
>> 5 files changed, 55 insertions(+), 48 deletions(-)
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index ae899f68551f..26238fb5e8cf 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -3727,6 +3727,43 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
>> }
>> EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
>>
>> +static int discover_region(struct device *dev, void *unused)
>> +{
>> + struct cxl_endpoint_decoder *cxled;
>> + int rc;
>> +
>> + if (!is_endpoint_decoder(dev))
>> + return 0;
>> +
>> + cxled = to_cxl_endpoint_decoder(dev);
>> + if ((cxled->cxld.flags & CXL_DECODER_F_ENABLE) == 0)
>> + return 0;
>> +
>> + if (cxled->state != CXL_DECODER_STATE_AUTO)
>> + return 0;
>> +
>> + /*
>> + * Region enumeration is opportunistic, if this add-event fails,
>> + * continue to the next endpoint decoder.
>> + */
>> + rc = cxl_add_to_region(cxled);
>> + if (rc)
>> + dev_dbg(dev, "failed to add to region: %#llx-%#llx\n",
>> + cxled->cxld.hpa_range.start, cxled->cxld.hpa_range.end);
>> +
>> + return 0;
>> +}
>> +
>> +int cxl_region_discovery(struct cxl_memdev *cxlmd)
>> +{
>> + struct cxl_port *port = cxlmd->endpoint;
>> +
>> + device_for_each_child(&port->dev, NULL, discover_region);
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_region_discovery, "CXL");
>> +
>> u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa)
>> {
>> struct cxl_region_ref *iter;
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index c796c3db36e0..86efcc4fb963 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -906,6 +906,7 @@ struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
>> int cxl_add_to_region(struct cxl_endpoint_decoder *cxled);
>> struct cxl_dax_region *to_cxl_dax_region(struct device *dev);
>> u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa);
>> +int cxl_region_discovery(struct cxl_memdev *cxlmd);
>> #else
>> static inline bool is_cxl_pmem_region(struct device *dev)
>> {
>> @@ -928,6 +929,10 @@ static inline u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint,
>> {
>> return 0;
>> }
>> +static inline int cxl_region_discovery(struct cxl_memdev *cxlmd)
>> +{
>> + return 0;
>> +}
>> #endif
>>
>> void cxl_endpoint_parse_cdat(struct cxl_port *port);
>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
>> index 333c366b69e7..7d19528d9b55 100644
>> --- a/drivers/cxl/mem.c
>> +++ b/drivers/cxl/mem.c
>> @@ -114,15 +114,6 @@ static int cxl_mem_probe(struct device *dev)
>> return -ENXIO;
>> }
>>
>> - if (cxl_pmem_size(cxlds) && IS_ENABLED(CONFIG_CXL_PMEM)) {
>> - rc = devm_cxl_add_nvdimm(parent_port, cxlmd);
>> - if (rc) {
>> - if (rc == -ENODEV)
>> - dev_info(dev, "PMEM disabled by platform\n");
>> - return rc;
>> - }
>> - }
>> -
>> if (dport->rch)
>> endpoint_parent = parent_port->uport_dev;
>> else
>> @@ -142,6 +133,15 @@ static int cxl_mem_probe(struct device *dev)
>> return rc;
>> }
>>
>> + if (cxl_pmem_size(cxlds) && IS_ENABLED(CONFIG_CXL_PMEM)) {
>> + rc = devm_cxl_add_nvdimm(parent_port, cxlmd);
>> + if (rc) {
>> + if (rc == -ENODEV)
>> + dev_info(dev, "PMEM disabled by platform\n");
>> + return rc;
>> + }
>> + }
>> +
>> if (cxlmd->attach) {
>> rc = cxlmd->attach->probe(cxlmd);
>> if (rc)
>> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
>> index 549368a9c868..70b40a10be7a 100644
>> --- a/drivers/cxl/pci.c
>> +++ b/drivers/cxl/pci.c
>> @@ -903,6 +903,7 @@ __ATTRIBUTE_GROUPS(cxl_rcd);
>> static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>> {
>> struct pci_host_bridge *host_bridge = pci_find_host_bridge(pdev->bus);
>> + struct cxl_memdev_attach memdev_attach = { 0 };
>> struct cxl_dpa_info range_info = { 0 };
>> struct cxl_memdev_state *mds;
>> struct cxl_dev_state *cxlds;
>> @@ -1006,7 +1007,8 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>> if (rc)
>> dev_dbg(&pdev->dev, "No CXL Features discovered\n");
>>
>> - cxlmd = devm_cxl_add_memdev(cxlds, NULL);
>> + memdev_attach.probe = cxl_region_discovery;
>> + cxlmd = devm_cxl_add_memdev(cxlds, &memdev_attach);
>> if (IS_ERR(cxlmd))
>> return PTR_ERR(cxlmd);
>>
>> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
>> index 7937e7e53797..fbeff1978bfb 100644
>> --- a/drivers/cxl/port.c
>> +++ b/drivers/cxl/port.c
>> @@ -30,33 +30,6 @@ static void schedule_detach(void *cxlmd)
>> schedule_cxl_memdev_detach(cxlmd);
>> }
>>
>> -static int discover_region(struct device *dev, void *unused)
>> -{
>> - struct cxl_endpoint_decoder *cxled;
>> - int rc;
>> -
>> - if (!is_endpoint_decoder(dev))
>> - return 0;
>> -
>> - cxled = to_cxl_endpoint_decoder(dev);
>> - if ((cxled->cxld.flags & CXL_DECODER_F_ENABLE) == 0)
>> - return 0;
>> -
>> - if (cxled->state != CXL_DECODER_STATE_AUTO)
>> - return 0;
>> -
>> - /*
>> - * Region enumeration is opportunistic, if this add-event fails,
>> - * continue to the next endpoint decoder.
>> - */
>> - rc = cxl_add_to_region(cxled);
>> - if (rc)
>> - dev_dbg(dev, "failed to add to region: %#llx-%#llx\n",
>> - cxled->cxld.hpa_range.start, cxled->cxld.hpa_range.end);
>> -
>> - return 0;
>> -}
>> -
>> static int cxl_switch_port_probe(struct cxl_port *port)
>> {
>> /* Reset nr_dports for rebind of driver */
>> @@ -82,17 +55,7 @@ static int cxl_endpoint_port_probe(struct cxl_port *port)
>> if (rc)
>> return rc;
>>
>> - rc = devm_cxl_endpoint_decoders_setup(port);
>> - if (rc)
>> - return rc;
>> -
>> - /*
>> - * Now that all endpoint decoders are successfully enumerated, try to
>> - * assemble regions from committed decoders
>> - */
>> - device_for_each_child(&port->dev, NULL, discover_region);
>> -
>> - return 0;
>> + return devm_cxl_endpoint_decoders_setup(port);
>> }
>>
>> static int cxl_port_probe(struct device *dev)
>
>