linux-kernel - [PATCH v2] cpu-topology: Skip the exist but not possible cpu nodes

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Date:   Sat, 11 Jan 2020 14:53:40 +0800
From:   Zeng Tao <prime.zeng@...ilicon.com>
To:     <sudeep.holla@....com>
CC:     <linuxarm@...wei.com>, Zeng Tao <prime.zeng@...ilicon.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] cpu-topology: Skip the exist but not possible cpu nodes

When CONFIG_NR_CPUS is smaller than the cpu nodes defined in the device
tree, all the cpu nodes parsing will fail.
And this is not reasonable for a legal device tree configs.
In this patch, skip such cpu nodes rather than return an error.
With CONFIG_NR_CPUS = 128 and cpus nodes num in device tree is 130,
The following warning messages will be print during boot:
CPU node for /cpus/cpu@128 exist but the possible cpu range is :0-127
CPU node for /cpus/cpu@129 exist but the possible cpu range is :0-127
CPU node for /cpus/cpu@130 exist but the possible cpu range is :0-127

Signed-off-by: Zeng Tao <prime.zeng@...ilicon.com>
---
Changelog:
v1->v2:
 -Remove redundant -ENODEV assignment in get_cpu_for_node
 -Add comment to describe the get_cpu_for_node return values
 -Add skip process for cpu threads
 -Update the commit log with more detail
---
 drivers/base/arch_topology.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 5fe44b3..01f0e21 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -248,22 +248,44 @@ core_initcall(free_raw_capacity);
 #endif
 
 #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
+/*
+ * This function returns the logic cpu number of the node.
+ * There are totally three kinds of return values:
+ * (1) logic cpu number which is > 0.
+ * (2) -ENDEV when the node is valid one which can be found in the device tree
+ * but there is no possible cpu nodes to match, when the CONFIG_NR_CPUS is
+ * smaller than cpus node numbers in device tree, this will happen. It's
+ * suggested to just ignore this case.
+ * (3) -EINVAL when other errors occur.
+ */
 static int __init get_cpu_for_node(struct device_node *node)
 {
-	struct device_node *cpu_node;
+	struct device_node *cpu_node, *t;
 	int cpu;
+	bool found = false;
 
 	cpu_node = of_parse_phandle(node, "cpu", 0);
 	if (!cpu_node)
-		return -1;
+		return -EINVAL;
+
+	for_each_of_cpu_node(t)
+		if (t == cpu_node) {
+			found = true;
+			break;
+		}
+
+	if (!found) {
+		pr_crit("Unable to find CPU node for %pOF\n", cpu_node);
+		return -EINVAL;
+	}
 
 	cpu = of_cpu_node_to_id(cpu_node);
 	if (cpu >= 0)
 		topology_parse_cpu_capacity(cpu_node, cpu);
 	else
-		pr_crit("Unable to find CPU node for %pOF\n", cpu_node);
+		pr_warn("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
+			cpu_node, cpumask_pr_args(cpu_possible_mask));
 
-	of_node_put(cpu_node);
 	return cpu;
 }
 
@@ -286,9 +308,8 @@ static int __init parse_core(struct device_node *core, int package_id,
 				cpu_topology[cpu].package_id = package_id;
 				cpu_topology[cpu].core_id = core_id;
 				cpu_topology[cpu].thread_id = i;
-			} else {
-				pr_err("%pOF: Can't get CPU for thread\n",
-				       t);
+			} else if (cpu != -ENODEV) {
+				pr_err("%pOF: Can't get CPU for thread\n", t);
 				of_node_put(t);
 				return -EINVAL;
 			}
@@ -307,7 +328,7 @@ static int __init parse_core(struct device_node *core, int package_id,
 
 		cpu_topology[cpu].package_id = package_id;
 		cpu_topology[cpu].core_id = core_id;
-	} else if (leaf) {
+	} else if (leaf && cpu != -ENODEV) {
 		pr_err("%pOF: Can't get CPU for leaf core\n", core);
 		return -EINVAL;
 	}
-- 
2.8.1