linux-kernel - [RFC PATCH v1 1/2] cxl/cli: add helpers to collect and sort regions by HPA

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Message-ID: <20251125143826.282312-2-pawel.mielimonka@fujitsu.com>
Date: Tue, 25 Nov 2025 23:38:23 +0900
From: Pawel Mielimonka <pawel.mielimonka@...itsu.com>
To: dan.j.williams@...el.com,
	alison.schofield@...el.com
Cc: Smita.KoralahalliChannabasappa@....com,
	linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	dave@...olabs.net,
	jonathan.cameron@...wei.com,
	dave.jiang@...el.com,
	vishal.l.verma@...el.com,
	ira.weiny@...el.com,
	Pawel Mielimonka <pawel.mielimonka@...itsu.com>
Subject: [RFC PATCH v1 1/2] cxl/cli: add helpers to collect and sort regions by HPA

Introduce cmp_region_hpa() and collect_regions_sorted() helpers to
enumerate CXL regions under a given decoder and sort them by their host
physical address.
These helpers will be used by the "cxl destroy-region" command to tear
down regions in HPA-descending order, i.e. in the reverse order of
region creation. This matches the decoder programming requirements from
the CXL specification (8.2.4.20.12 - continuous HPA coverage at all
times when Lock On Commit is used) and avoids teardown sequences that
can leve decoder state inconsistent when the decoder is fully populated
(known problem).
This patch only adds the helpers; no functional changes is intended yet.

Signed-off-by: Pawel Mielimonka <pawel.mielimonka@...itsu.com>
---
 cxl/region.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/cxl/region.c b/cxl/region.c
index 207cf2d0..58765b3d 100644
--- a/cxl/region.c
+++ b/cxl/region.c
@@ -831,6 +831,61 @@ out:
 	return cxl_region_disable(region);
 }
 
+static int cmp_region_hpa(const void *l, const void *r)
+{
+	const struct cxl_region *const *left = l;
+	const struct cxl_region *const *right = r;
+	u64 left_start = cxl_region_get_resource((struct cxl_region *) *left);
+	u64 right_start = cxl_region_get_resource((struct cxl_region *) *right);
+
+	if (left_start < right_start)
+		return -1;
+	if (left_start > right_start)
+		return 1;
+	return 0;
+}
+
+static int collect_regions_sorted(struct cxl_decoder *root,
+								  const char *filter,
+								  struct cxl_region ***out,
+								  int *out_nr)
+{
+	struct cxl_region *region;
+	struct cxl_region **list = NULL;
+	int nr = 0, alloc = 0;
+
+	cxl_region_foreach(root, region) {
+		if (filter && !util_cxl_region_filter(region, filter))
+			continue;
+		if (nr == alloc) {
+			int new_alloc = alloc ? alloc * 2 : 8;
+			int new_size = (size_t)new_alloc * sizeof(*list);
+			struct cxl_region **tmp;
+
+			tmp = realloc(list, new_size);
+			if (!tmp) {
+				free(list);
+				return -ENOMEM;
+			}
+			list = tmp;
+			alloc = new_alloc;
+		}
+		list[nr++] = region;
+	}
+
+	if (!nr) {
+		free(list);
+		*out = NULL;
+		*out_nr = 0;
+		return 0;
+	}
+
+	qsort(list, nr, sizeof(*list), cmp_region_hpa);
+	*out = list;
+	*out_nr = nr;
+	return 0;
+}
+
 static int destroy_region(struct cxl_region *region)
 {
 	const char *devname = cxl_region_get_devname(region);
-- 
2.45.1.windows.1