[RFC PATCH 4/8] arch_numa: Avoid onlining empty NUMA nodes

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
To: Dan Williams <dan.j.williams@intel.com>,
	<linux-cxl@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	Sudeep Holla <sudeep.holla@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Will Deacon <will@kernel.org>, Jia He <justin.he@arm.com>,
	Mike Rapoport <rppt@linux.ibm.com>, <linuxarm@huawei.com>,
	<catalin.marinas@arm.com>, <Anshuman.Khandual@arm.com>,
	Yuquan Wang <wangyuquan1236@phytium.com.cn>,
	Oscar Salvador <osalvador@suse.de>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	James Morse <james.morse@arm.com>
Subject: [RFC PATCH 4/8] arch_numa: Avoid onlining empty NUMA nodes
Date: Wed, 29 May 2024 18:12:32 +0100	[thread overview]
Message-ID: <20240529171236.32002-5-Jonathan.Cameron@huawei.com> (raw)
In-Reply-To: <20240529171236.32002-1-Jonathan.Cameron@huawei.com>

ACPI can declare NUMA nodes for memory that will be along later.
CXL Fixed Memory Windows may also be assigned NUMA nodes that
are initially empty.  Currently the generic arch_numa handling will
online these empty nodes. This is both inconsistent with x86 and
with itself as if we add memory and remove it again the node goes
away.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/base/arch_numa.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/base/arch_numa.c b/drivers/base/arch_numa.c
index 5b59d133b6af..0630efb696ab 100644
--- a/drivers/base/arch_numa.c
+++ b/drivers/base/arch_numa.c
@@ -363,6 +363,11 @@ static int __init numa_register_nodes(void)
 		unsigned long start_pfn, end_pfn;
 
 		get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
+		if (start_pfn >= end_pfn &&
+		    !node_state(nid, N_CPU) &&
+		    !node_state(nid, N_GENERIC_INITIATOR))
+			continue;
+
 		setup_node_data(nid, start_pfn, end_pfn);
 		node_set_online(nid);
 	}
-- 
2.39.2


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