Re: [PATCH v5 4/7] cxl/region: Add helper to check Soft Reserved containment by CXL regions

[Koralahalli Channabasappa, Smita]

On 1/23/2026 2:19 PM, Dave Jiang wrote:

On 1/21/26 9:55 PM, Smita Koralahalli wrote:

Add a helper to determine whether a given Soft Reserved memory range is
fully contained within the committed CXL region.

This helper provides a primitive for policy decisions in subsequent
patches such as co-ordination with dax_hmem to determine whether CXL has
fully claimed ownership of Soft Reserved memory ranges.

No functional changes are introduced by this patch.

Signed-off-by: Smita Koralahalli <smita.koralahallichannabasa...@amd.com>

Reviewed-by: Dave Jiang <dave.ji...@intel.com>

Just a nit below.

Thank you Jonathan and Dave for the review.

---
  drivers/cxl/core/region.c | 29 +++++++++++++++++++++++++++++
  drivers/cxl/cxl.h         |  5 +++++
  2 files changed, 34 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 45ee598daf95..9827a6dd3187 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3875,6 +3875,35 @@ static int cxl_region_debugfs_poison_clear(void *data, 
u64 offset)
  DEFINE_DEBUGFS_ATTRIBUTE(cxl_poison_clear_fops, NULL,
                         cxl_region_debugfs_poison_clear, "%llx\n");

+static int cxl_region_contains_sr_cb(struct device *dev, void *data)

Since it's a local helper, maybe just call it region_contains_soft_reserve()?

Okay I will rename in next revision.

Thanks
Smita

DJ

+{
+       struct resource *res = data;
+       struct cxl_region *cxlr;
+       struct cxl_region_params *p;
+
+       if (!is_cxl_region(dev))
+               return 0;
+
+       cxlr = to_cxl_region(dev);
+       p = &cxlr->params;
+
+       if (p->state != CXL_CONFIG_COMMIT)
+               return 0;
+
+       if (!p->res)
+               return 0;
+
+       return resource_contains(p->res, res) ? 1 : 0;
+}
+
+bool cxl_region_contains_soft_reserve(const struct resource *res)
+{
+       guard(rwsem_read)(&cxl_rwsem.region);
+       return bus_for_each_dev(&cxl_bus_type, NULL, (void *)res,
+                               cxl_region_contains_sr_cb) != 0;
+}
+EXPORT_SYMBOL_GPL(cxl_region_contains_soft_reserve);
+
  static int cxl_region_can_probe(struct cxl_region *cxlr)
  {
        struct cxl_region_params *p = &cxlr->params;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index c796c3db36e0..b0ff6b65ea0b 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);
+bool cxl_region_contains_soft_reserve(const struct resource *res);
  #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 bool cxl_region_contains_soft_reserve(const struct resource *res)
+{
+       return false;
+}
  #endif

void cxl_endpoint_parse_cdat(struct cxl_port *port);