linux-kernel - [PATCH v3 2/2] ACPI: NUMA: debug invalid unused PXM value for CFMWs

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Message-Id: <20250317101533.2582624-3-wangyuquan1236@phytium.com.cn>
Date: Mon, 17 Mar 2025 18:15:33 +0800
From: Yuquan Wang <wangyuquan1236@...tium.com.cn>
To: Jonathan.Cameron@...wei.com,
	dan.j.williams@...el.com,
	rppt@...nel.org,
	akpm@...ux-foundation.org,
	david@...hat.com,
	bfaccini@...dia.com,
	rafael@...nel.org,
	lenb@...nel.org,
	dave@...olabs.net,
	dave.jiang@...el.com,
	alison.schofield@...el.com,
	vishal.l.verma@...el.com,
	ira.weiny@...el.com,
	rrichter@....com,
	haibo1.xu@...el.com
Cc: linux-acpi@...r.kernel.org,
	linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chenbaozi@...tium.com.cn,
	Yuquan Wang <wangyuquan1236@...tium.com.cn>
Subject: [PATCH v3 2/2] ACPI: NUMA: debug invalid unused PXM value for CFMWs

The absence of SRAT would cause the fake_pxm to be -1 and increment
to 0, then send to acpi_parse_cfmws(). If there exists CXL memory
ranges that are defined in the CFMWS and not already defined in the
SRAT, the new node (node0) for the CXL memory would be invalid, as
node0 is already in "used", and all CXL memory might be online on
node0.

This utilizes node_set(0, nodes_found_map) to set pxm&node map. With
this setting, acpi_map_pxm_to_node() could return the expected node
value even if no SRAT.

If SRAT is valid, the numa_memblks_init() would then utilize
numa_move_tail_memblk() to move the numa_memblk from numa_meminfo to
numa_reserved_meminfo in CFMWs fake node situation.

If SRAT is missing or bad, the numa_memblks_init() would fail since
init_func() would fail. And it causes that no numa_memblk in
numa_reserved_meminfo list and the following dax_cxl driver could
find the expected fake node.

Use numa_add_reserved_memblk() to replace numa_add_memblk(), since
the cxl numa_memblk added by numa_add_memblk() would finally be moved
to numa_reserved_meminfo, and numa_add_reserved_memblk() here could
add cxl numa_memblk into reserved list directly. Hence, no matter
SRAT is good or not, cxl numa_memblk could be allocated to reserved
list.

Signed-off-by: Yuquan Wang <wangyuquan1236@...tium.com.cn>
---
 drivers/acpi/numa/srat.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
index 00ac0d7bb8c9..50bfecfb9c16 100644
--- a/drivers/acpi/numa/srat.c
+++ b/drivers/acpi/numa/srat.c
@@ -458,11 +458,12 @@ static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
 		return -EINVAL;
 	}

-	if (numa_add_memblk(node, start, end) < 0) {
+	if (numa_add_reserved_memblk(node, start, end) < 0) {
 		/* CXL driver must handle the NUMA_NO_NODE case */
 		pr_warn("ACPI NUMA: Failed to add memblk for CFMWS node %d [mem %#llx-%#llx]\n",
 			node, start, end);
 	}
+
 	node_set(node, numa_nodes_parsed);

 	/* Set the next available fake_pxm value */
@@ -646,8 +647,12 @@ int __init acpi_numa_init(void)
 		if (node_to_pxm_map[i] > fake_pxm)
 			fake_pxm = node_to_pxm_map[i];
 	}
-	last_real_pxm = fake_pxm;
-	fake_pxm++;
+
+	/* Make sure CFMWs fake node >= 1 */
+	fake_pxm = max(fake_pxm, 0);
+	last_real_pxm = fake_pxm++;
+	node_set(0, nodes_found_map);
+
 	acpi_table_parse_cedt(ACPI_CEDT_TYPE_CFMWS, acpi_parse_cfmws,
 			      &fake_pxm);

-- 
2.34.1