[PATCH v4 02/27] cxl/regs: Skip sub-block region request for BAR-owning drivers
From: mhonap
Date: Thu Aug 13 2026 - 05:40:16 EST
From: Manish Honap <mhonap@xxxxxxxxxx>
cxl_map_component_regs() claims each mapped sub-block with
devm_request_mem_region(). A driver that owns the whole component
register BAR, such as vfio-cxl, has already claimed the full BAR, so
the per-sub-block claim collides and the mapping fails.
Add a bar_owned parameter to cxl_pci_setup_regs() and record it in
skip_sub_bar_request on the register map. When set, cxl-core maps the
sub-block without requesting the region and leaves ownership with the
upper driver. cxl_pci passes false and keeps its existing claim,
preserving /dev/mem tooling access to the rest of the component space.
Signed-off-by: Manish Honap <mhonap@xxxxxxxxxx>
---
drivers/cxl/core/pci.c | 9 ++++++++-
drivers/cxl/core/regs.c | 32 ++++++++++++++++++++++----------
drivers/cxl/pci.c | 4 ++--
include/cxl/cxl.h | 3 +++
include/cxl/pci.h | 2 +-
5 files changed, 36 insertions(+), 14 deletions(-)
diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 9d807c1a002c..08d4c955137d 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -720,7 +720,7 @@ static int cxl_rcrb_get_comp_regs(struct pci_dev *pdev,
}
int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
- struct cxl_register_map *map)
+ struct cxl_register_map *map, bool bar_owned)
{
int rc;
@@ -750,6 +750,13 @@ int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
return rc;
}
+ /*
+ * A caller that owns the whole register BAR (for example vfio-cxl)
+ * maps the sub-blocks without claiming them, so the later
+ * cxl_map_component_regs() does not collide with the full-BAR request.
+ */
+ map->skip_sub_bar_request = bar_owned;
+
return cxl_setup_regs(map);
}
EXPORT_SYMBOL_NS_GPL(cxl_pci_setup_regs, "CXL");
diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
index 989e79383b99..90dd85f322f5 100644
--- a/drivers/cxl/core/regs.c
+++ b/drivers/cxl/core/regs.c
@@ -177,35 +177,47 @@ void cxl_probe_device_regs(struct device *dev, void __iomem *base,
}
EXPORT_SYMBOL_NS_GPL(cxl_probe_device_regs, "CXL");
-void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
- resource_size_t length)
+static void __iomem *__cxl_iomap_block(struct device *dev, resource_size_t addr,
+ resource_size_t length, bool request)
{
+ resource_size_t end = addr + length - 1;
void __iomem *ret_val;
struct resource *res;
if (WARN_ON_ONCE(addr == CXL_RESOURCE_NONE))
return NULL;
- res = devm_request_mem_region(dev, addr, length, dev_name(dev));
- if (!res) {
- resource_size_t end = addr + length - 1;
-
- dev_err(dev, "Failed to request region %pa-%pa\n", &addr, &end);
- return NULL;
+ /*
+ * An owning driver (e.g. vfio-cxl) may already hold the whole BAR; a
+ * sub-block request would then collide with that claim.
+ */
+ if (request) {
+ res = devm_request_mem_region(dev, addr, length, dev_name(dev));
+ if (!res) {
+ dev_err(dev, "Failed to request region %pa-%pa\n", &addr, &end);
+ return NULL;
+ }
}
ret_val = devm_ioremap(dev, addr, length);
if (!ret_val)
- dev_err(dev, "Failed to map region %pr\n", res);
+ dev_err(dev, "Failed to map region %pa-%pa\n", &addr, &end);
return ret_val;
}
+
+void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
+ resource_size_t length)
+{
+ return __cxl_iomap_block(dev, addr, length, true);
+}
EXPORT_SYMBOL_NS_GPL(devm_cxl_iomap_block, "CXL");
int cxl_map_component_regs(const struct cxl_register_map *map,
struct cxl_component_regs *regs,
unsigned long map_mask)
{
+ bool request = !map->skip_sub_bar_request;
struct device *host = map->host;
struct mapinfo {
const struct cxl_reg_map *rmap;
@@ -227,7 +239,7 @@ int cxl_map_component_regs(const struct cxl_register_map *map,
continue;
addr = map->resource + mi->rmap->offset;
length = mi->rmap->size;
- *(mi->addr) = devm_cxl_iomap_block(host, addr, length);
+ *(mi->addr) = __cxl_iomap_block(host, addr, length, request);
if (!*(mi->addr))
return -ENOMEM;
}
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index bb892dbfdd6d..ec1693c21f61 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -816,7 +816,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
cxlds->rcd = is_cxl_restricted(pdev);
- rc = cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map);
+ rc = cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map, false);
if (rc)
return rc;
@@ -829,7 +829,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
* still be useful for management functions so don't return an error.
*/
rc = cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_COMPONENT,
- &cxlds->reg_map);
+ &cxlds->reg_map, false);
if (rc)
dev_warn(&pdev->dev, "No component registers (%d)\n", rc);
else if (!cxlds->reg_map.component_map.ras.valid)
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index efb8ac97bd92..f8e8fddba152 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -213,6 +213,8 @@ struct cxl_pmu_reg_map {
* @resource: physical resource base of the register block
* @max_size: maximum mapping size to perform register search
* @reg_type: see enum cxl_regloc_type
+ * @skip_sub_bar_request: set via cxl_pci_setup_regs(); the owning driver holds
+ * the BAR, so skip the sub-block claim
* @component_map: cxl_reg_map for component registers
* @device_map: cxl_reg_maps for device registers
* @pmu_map: cxl_reg_maps for CXL Performance Monitoring Units
@@ -223,6 +225,7 @@ struct cxl_register_map {
resource_size_t resource;
resource_size_t max_size;
u8 reg_type;
+ bool skip_sub_bar_request;
union {
struct cxl_component_reg_map component_map;
struct cxl_device_reg_map device_map;
diff --git a/include/cxl/pci.h b/include/cxl/pci.h
index 3e0000015871..81a32004a604 100644
--- a/include/cxl/pci.h
+++ b/include/cxl/pci.h
@@ -18,5 +18,5 @@ struct cxl_register_map;
struct pci_dev;
int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
- struct cxl_register_map *map);
+ struct cxl_register_map *map, bool bar_owned);
#endif
--
2.25.1