linux-kernel - [RFC v2 05/15] cxl: introduce cxl_get_committed

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Message-ID: <20251209165019.2643142-6-mhonap@nvidia.com>
Date: Tue, 9 Dec 2025 22:20:09 +0530
From: <mhonap@...dia.com>
To: <aniketa@...dia.com>, <ankita@...dia.com>, <alwilliamson@...dia.com>,
	<vsethi@...dia.com>, <jgg@...dia.com>, <mochs@...dia.com>,
	<skolothumtho@...dia.com>, <alejandro.lucero-palau@....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>, <dan.j.williams@...el.com>, <jgg@...pe.ca>,
	<yishaih@...dia.com>, <kevin.tian@...el.com>
CC: <cjia@...dia.com>, <kwankhede@...dia.com>, <targupta@...dia.com>,
	<zhiw@...dia.com>, <kjaju@...dia.com>, <linux-kernel@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, <kvm@...r.kernel.org>, <mhonap@...dia.com>
Subject: [RFC v2 05/15] cxl: introduce cxl_get_committed_regions()

From: Zhi Wang <zhiw@...dia.com>

The kernel CXL core can discover the configured and committed CXL regions
from BIOS or firmware, respect its configuration and create the related
kernel CXL core data structures without configuring and committing the CXL
region.

However, those information are kept within the kernel CXL core. A type-2
device can have the same usage and a type-2 driver would like to know
about it before creating the CXL regions.

Introduce cxl_get_committed_regions() for a type-2 driver to discover the
committed regions.

Signed-off-by: Zhi Wang <zhiw@...dia.com>
Signed-off-by: Manish Honap <mhonap@...dia.com>
---
 drivers/cxl/core/region.c | 73 +++++++++++++++++++++++++++++++++++++++
 include/cxl/cxl.h         |  1 +
 2 files changed, 74 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index e89a98780e76..6c368b4641f1 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2785,6 +2785,79 @@ int cxl_get_region_range(struct cxl_region *region, struct range *range)
 }
 EXPORT_SYMBOL_NS_GPL(cxl_get_region_range, "CXL");
 
+struct match_region_info {
+	struct cxl_memdev *cxlmd;
+	struct cxl_region **cxlrs;
+	int nr_regions;
+};
+
+static int match_region_by_device(struct device *match, void *data)
+{
+	struct match_region_info *info = data;
+	struct cxl_endpoint_decoder *cxled;
+	struct cxl_memdev *cxlmd;
+	struct cxl_region_params *p;
+	struct cxl_region *cxlr;
+	int i;
+
+	if (!is_cxl_region(match))
+		return 0;
+
+	lockdep_assert_held(&cxl_rwsem.region);
+	cxlr = to_cxl_region(match);
+	p = &cxlr->params;
+
+	if (p->state != CXL_CONFIG_COMMIT)
+		return 0;
+
+	for (i = 0; i < p->nr_targets; i++) {
+		void *cxlrs;
+
+		cxled = p->targets[i];
+		cxlmd = cxled_to_memdev(cxled);
+
+		if (info->cxlmd != cxlmd)
+			continue;
+
+		cxlrs = krealloc(info->cxlrs, sizeof(cxlr) * (info->nr_regions + 1),
+				 GFP_KERNEL);
+		if (!cxlrs) {
+			kfree(info->cxlrs);
+			return -ENOMEM;
+		}
+		info->cxlrs = cxlrs;
+
+		info->cxlrs[info->nr_regions++] = cxlr;
+	}
+
+	return 0;
+}
+
+int cxl_get_committed_regions(struct cxl_memdev *cxlmd, struct cxl_region ***cxlrs, int *num)
+{
+	struct match_region_info info = {0};
+	int ret = 0;
+
+	ret = down_write_killable(&cxl_rwsem.region);
+	if (ret)
+		return ret;
+
+	info.cxlmd = cxlmd;
+
+	ret = bus_for_each_dev(&cxl_bus_type, NULL, &info, match_region_by_device);
+	if (ret) {
+		kfree(info.cxlrs);
+	} else {
+		*cxlrs = info.cxlrs;
+		*num = info.nr_regions;
+	}
+
+	up_write(&cxl_rwsem.region);
+
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_get_committed_regions, "CXL");
+
 static ssize_t __create_region_show(struct cxl_root_decoder *cxlrd, char *buf)
 {
 	return sysfs_emit(buf, "region%u\n", atomic_read(&cxlrd->region_id));
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index e3bf8cf0b6d6..0a1f245557f4 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -295,5 +295,6 @@ int cxl_get_region_range(struct cxl_region *region, struct range *range);
 int cxl_get_hdm_reg_info(struct cxl_dev_state *cxlds, u64 *count, u64 *offset,
 			 u64 *size);
 int cxl_find_comp_regblock_offset(struct pci_dev *pdev, u64 *offset);
+int cxl_get_committed_regions(struct cxl_memdev *cxlmd, struct cxl_region ***cxlrs, int *num);
 
 #endif /* __CXL_CXL_H__ */
-- 
2.25.1