[PATCH 18/19] cxl/region: Define a driver interface for region creation

[Dan Williams <dan.j.williams@intel.com>]

Scenarios like recreating persistent memory regions from label data and
establishing new regions for CXL attached accelerators with local memory
need a kernel internal facility to establish new regions.

Introduce cxl_create_region() that takes an array of endpoint decoders
with reserved capacity and a root decoder object to establish a new
region.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/core/region.c |  107 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/cxl/cxlmem.h      |    3 +
 2 files changed, 110 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index a41756249f8d..543c4499379e 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2878,6 +2878,104 @@ construct_region_begin(struct cxl_root_decoder *cxlrd,
 	return cxlr;
 }
 
+static struct cxl_region *
+__construct_new_region(struct cxl_root_decoder *cxlrd,
+		       struct cxl_endpoint_decoder **cxled, int ways)
+{
+	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
+	struct cxl_region_params *p;
+	resource_size_t size = 0;
+	struct cxl_region *cxlr;
+	int rc, i;
+
+	if (ways < 1)
+		return ERR_PTR(-EINVAL);
+
+	cxlr = construct_region_begin(cxlrd, cxled[0]);
+	if (IS_ERR(cxlr))
+		return cxlr;
+
+	rc = set_interleave_ways(cxlr, ways);
+	if (rc)
+		goto out;
+
+	rc = set_interleave_granularity(cxlr, cxld->interleave_granularity);
+	if (rc)
+		goto out;
+
+	down_read(&cxl_dpa_rwsem);
+	for (i = 0; i < ways; i++) {
+		if (!cxled[i]->dpa_res)
+			break;
+		size += resource_size(cxled[i]->dpa_res);
+	}
+	up_read(&cxl_dpa_rwsem);
+
+	if (i < ways)
+		goto out;
+
+	rc = alloc_hpa(cxlr, size);
+	if (rc)
+		goto out;
+
+	down_read(&cxl_dpa_rwsem);
+	for (i = 0; i < ways; i++) {
+		rc = cxl_region_attach(cxlr, cxled[i], i);
+		if (rc)
+			break;
+	}
+	up_read(&cxl_dpa_rwsem);
+
+	if (rc)
+		goto out;
+
+	rc = cxl_region_decode_commit(cxlr);
+	if (rc)
+		goto out;
+
+	p = &cxlr->params;
+	p->state = CXL_CONFIG_COMMIT;
+out:
+	construct_region_end();
+	if (rc) {
+		drop_region(cxlr);
+		return ERR_PTR(rc);
+	}
+	return cxlr;
+}
+
+/**
+ * cxl_create_region - Establish a region given an array of endpoint decoders
+ * @cxlrd: root decoder to allocate HPA
+ * @cxled: array of endpoint decoders with reserved DPA capacity
+ * @ways: size of @cxled array
+ *
+ * Returns a fully formed region in the commit state and attached to the
+ * cxl_region driver.
+ */
+struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
+				     struct cxl_endpoint_decoder **cxled,
+				     int ways)
+{
+	struct cxl_region *cxlr;
+
+	mutex_lock(&cxlrd->range_lock);
+	cxlr = __construct_new_region(cxlrd, cxled, ways);
+	mutex_unlock(&cxlrd->range_lock);
+
+	if (IS_ERR(cxlr))
+		return cxlr;
+
+	if (device_attach(&cxlr->dev) <= 0) {
+		dev_err(&cxlr->dev, "failed to create region\n");
+		drop_region(cxlr);
+		return ERR_PTR(-ENODEV);
+	}
+
+	return cxlr;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_create_region, CXL);
+
 /* Establish an empty region covering the given HPA range */
 static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 					   struct cxl_endpoint_decoder *cxled)
@@ -3085,6 +3183,15 @@ static int cxl_region_probe(struct device *dev)
 					p->res->start, p->res->end, cxlr,
 					is_system_ram) > 0)
 			return 0;
+
+		/*
+		 * HDM-D[B] (device-memory) regions have accelerator
+		 * specific usage, skip device-dax registration.
+		 */
+		if (cxlr->type == CXL_DECODER_DEVMEM)
+			return 0;
+
+		/* HDM-H routes to device-dax */
 		return devm_cxl_add_dax_region(cxlr);
 	default:
 		dev_dbg(&cxlr->dev, "unsupported region mode: %d\n",
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 69f07186502d..ad7f806549d3 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -98,6 +98,9 @@ struct cxl_root_decoder *cxl_hpa_freespace(struct cxl_port *endpoint,
 					   int interleave_ways,
 					   unsigned long flags,
 					   resource_size_t *max);
+struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
+				     struct cxl_endpoint_decoder **cxled,
+				     int ways);
 
 static inline struct cxl_ep *cxl_ep_load(struct cxl_port *port,
 					 struct cxl_memdev *cxlmd)