linux-kernel - [PATCH 5/6] dax/hmem: Reintroduce Soft Reserved ranges back into the iomem tree

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Message-ID: <20250822034202.26896-6-Smita.KoralahalliChannabasappa@amd.com>
Date: Fri, 22 Aug 2025 03:42:01 +0000
From: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <linux-fsdevel@...r.kernel.org>,
	<linux-pm@...r.kernel.org>
CC: Davidlohr Bueso <dave@...olabs.net>, Jonathan Cameron
	<jonathan.cameron@...wei.com>, Dave Jiang <dave.jiang@...el.com>, "Alison
 Schofield" <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Matthew Wilcox <willy@...radead.org>, Jan Kara
	<jack@...e.cz>, "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown
	<len.brown@...el.com>, Pavel Machek <pavel@...nel.org>, Li Ming
	<ming.li@...omail.com>, Jeff Johnson <jeff.johnson@....qualcomm.com>, "Ying
 Huang" <huang.ying.caritas@...il.com>, Yao Xingtao <yaoxt.fnst@...itsu.com>,
	Peter Zijlstra <peterz@...radead.org>, Greg KH <gregkh@...uxfoundation.org>,
	Nathan Fontenot <nathan.fontenot@....com>, Smita Koralahalli
	<Smita.KoralahalliChannabasappa@....com>, Terry Bowman
	<terry.bowman@....com>, Robert Richter <rrichter@....com>, Benjamin Cheatham
	<benjamin.cheatham@....com>, PradeepVineshReddy Kodamati
	<PradeepVineshReddy.Kodamati@....com>, Zhijian Li <lizhijian@...itsu.com>
Subject: [PATCH 5/6] dax/hmem: Reintroduce Soft Reserved ranges back into the iomem tree

Reworked from a patch by Alison Schofield <alison.schofield@...el.com>

Reintroduce Soft Reserved range into the iomem_resource tree for dax_hmem
to consume.

This restores visibility in /proc/iomem for ranges actively in use, while
avoiding the early-boot conflicts that occurred when Soft Reserved was
published into iomem before CXL window and region discovery.

Link: https://lore.kernel.org/linux-cxl/29312c0765224ae76862d59a17748c8188fb95f1.1692638817.git.alison.schofield@intel.com/
Co-developed-by: Alison Schofield <alison.schofield@...el.com>
Signed-off-by: Alison Schofield <alison.schofield@...el.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
---
 drivers/dax/hmem/hmem.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
index 90978518e5f4..24a6e7e3d916 100644
--- a/drivers/dax/hmem/hmem.c
+++ b/drivers/dax/hmem/hmem.c
@@ -93,6 +93,40 @@ static void process_defer_work(struct work_struct *_work)
 	walk_hmem_resources(&pdev->dev, handle_deferred_cxl);
 }
 
+static void remove_soft_reserved(void *data)
+{
+	struct resource *r = data;
+
+	remove_resource(r);
+	kfree(r);
+}
+
+static int add_soft_reserve_into_iomem(struct device *host,
+				       const struct resource *res)
+{
+	struct resource *soft = kzalloc(sizeof(*soft), GFP_KERNEL);
+	int rc;
+
+	if (!soft)
+		return -ENOMEM;
+
+	*soft = DEFINE_RES_NAMED_DESC(res->start, (res->end - res->start + 1),
+				      "Soft Reserved", IORESOURCE_MEM,
+				      IORES_DESC_SOFT_RESERVED);
+
+	rc = insert_resource(&iomem_resource, soft);
+	if (rc) {
+		kfree(soft);
+		return rc;
+	}
+
+	rc = devm_add_action_or_reset(host, remove_soft_reserved, soft);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
 static int hmem_register_device(struct device *host, int target_nid,
 				const struct resource *res)
 {
@@ -125,6 +159,10 @@ static int hmem_register_device(struct device *host, int target_nid,
 					    IORES_DESC_SOFT_RESERVED);
 	if (rc != REGION_INTERSECTS)
 		return 0;
+
+	rc = add_soft_reserve_into_iomem(host, res);
+	if (rc)
+		return rc;
 #else
 	rc = region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
 			       IORES_DESC_SOFT_RESERVED);
-- 
2.17.1