[PATCH v6 4/6] cxl/region: Provide region info to the cxl_poison trace event

[alison . schofield]

From: Alison Schofield <alison.schofield@xxxxxxxxx>

User space may need to know which region, if any, maps the poison
address(es) logged in a cxl_poison trace event. Since the mapping
of DPAs (device physical addresses) to a region can change, the
kernel must provide this information at the time the poison list
is read. The event informs user space that at event <timestamp>
this <region> mapped to this <DPA>, which is poisoned.

The cxl_poison trace event is already wired up to log the region
name and uuid if it receives param 'struct cxl_region'.

In order to provide that cxl_region, add another method for gathering
poison - by committed endpoint decoder mappings. This method is only
available with CONFIG_CXL_REGION and is only used if a region actually
maps the memdev where poison is being read. The default method remains:
read the poison by memdev resource.

Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
---
 drivers/cxl/core/core.h   |  5 +++
 drivers/cxl/core/memdev.c | 14 ++++++-
 drivers/cxl/core/region.c | 82 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 100 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 8c04672dca56..2f9bd8651eb1 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -22,7 +22,12 @@ void cxl_decoder_kill_region(struct cxl_endpoint_decoder *cxled);
 #define CXL_PMEM_REGION_TYPE(x) (&cxl_pmem_region_type)
 int cxl_region_init(void);
 void cxl_region_exit(void);
+int cxl_get_poison_by_endpoint(struct device *dev, void *data);
 #else
+static inline int cxl_get_poison_by_endpoint(struct device *dev, void *data)
+{
+	return 0;
+}
 static inline void cxl_decoder_kill_region(struct cxl_endpoint_decoder *cxled)
 {
 }
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index 19b833c9cf35..8696d7b508b6 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -139,14 +139,26 @@ static ssize_t trigger_poison_list_store(struct device *dev,
 					 const char *buf, size_t len)
 {
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_port *port;
 	bool trigger;
 	int rc;
 
 	if (kstrtobool(buf, &trigger) || !trigger)
 		return -EINVAL;
 
+	port = dev_get_drvdata(&cxlmd->dev);
+	if (!port || !is_cxl_endpoint(port))
+		return -EINVAL;
+
 	down_read(&cxl_dpa_rwsem);
-	rc = cxl_get_poison_by_memdev(cxlmd);
+	if (port->commit_end == -1)
+		/* No regions mapped to this memdev */
+		rc = cxl_get_poison_by_memdev(cxlmd);
+	else
+		/* Regions mapped, collect poison by endpoint */
+		rc = device_for_each_child(&port->dev, port,
+					   cxl_get_poison_by_endpoint);
+
 	up_read(&cxl_dpa_rwsem);
 
 	return rc ? rc : len;
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 67e83d961670..0ac08e9106af 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1826,6 +1826,88 @@ struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(to_cxl_pmem_region, CXL);
 
+int cxl_get_poison_by_endpoint(struct device *dev, void *data)
+{
+	struct cxl_endpoint_decoder *cxled;
+	struct cxl_port *port = data;
+	struct cxl_dev_state *cxlds;
+	struct cxl_memdev *cxlmd;
+	u64 offset, length;
+	int rc = 0;
+
+	down_read(&cxl_dpa_rwsem);
+
+	if (!is_endpoint_decoder(dev))
+		goto out;
+
+	cxled = to_cxl_endpoint_decoder(dev);
+	if (!cxled->dpa_res || !resource_size(cxled->dpa_res))
+		goto out;
+
+	/*
+	 * Get the poison by decoder for mapped resources. This
+	 * separates pmem and ram poison list reads, as the spec
+	 * requires, and provides the region for the trace event.
+	 */
+	cxlmd = cxled_to_memdev(cxled);
+	length = cxled->dpa_res->end - cxled->dpa_res->start + 1;
+	rc = cxl_mem_get_poison(cxlmd, cxled->dpa_res->start, length,
+				cxled->cxld.region);
+	if (rc == -EFAULT && cxled->mode == CXL_DECODER_RAM)
+		rc = 0;
+	if (rc)
+		goto out;
+
+	/* Get poison in a skip range */
+	if (cxled->skip) {
+		rc = cxl_mem_get_poison(cxlmd, 0, cxled->skip, NULL);
+		if (rc == -EFAULT && cxled->mode == CXL_DECODER_RAM)
+			rc = 0;
+		if (rc)
+			goto out;
+	}
+
+	/* Iterate until commit_end is reached */
+	if (cxled->cxld.id < port->commit_end)
+		goto out;
+
+	/*
+	 * Reach here with the last committed decoder only.
+	 * Knowing that PMEM must always follow RAM, get poison
+	 * for unmapped ranges based on the last decoder's mode:
+	 *	ram: scan remains of ram range, then scan for pmem
+	 *	pmem: scan remains of pmem range
+	 */
+	cxlds = cxlmd->cxlds;
+
+	if (cxled->mode == CXL_DECODER_RAM) {
+		offset = cxled->dpa_res->end + 1;
+		length = resource_size(&cxlds->ram_res) - offset;
+		rc = cxl_mem_get_poison(cxlmd, offset, length, NULL);
+		if (rc == -EFAULT)
+			rc = 0;
+		if (rc)
+			goto out;
+	}
+	if (cxled->mode == CXL_DECODER_PMEM) {
+		offset = cxled->dpa_res->end + 1;
+		length = resource_size(&cxlds->pmem_res) - offset;
+	} else if (resource_size(&cxlds->pmem_res)) {
+		offset = cxlds->pmem_res.start;
+		length = resource_size(&cxlds->pmem_res);
+	} else {
+		rc = 1;
+		goto out;
+	}
+	/* Final get poison call. Return rc or 1 to stop iteration. */
+	rc = cxl_mem_get_poison(cxlmd, offset, length, NULL);
+	if (!rc)
+		rc = 1;
+out:
+	up_read(&cxl_dpa_rwsem);
+	return rc;
+}
+
 static struct lock_class_key cxl_pmem_region_key;
 
 static struct cxl_pmem_region *cxl_pmem_region_alloc(struct cxl_region *cxlr)
-- 
2.37.3