linux-kernel - [PATCH v2] PM: EM: Fix potential division-by-zero error in em_compute

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Message-ID: <tencent_EE27C7D1D6BDB3EE57A2C467CC59A866C405@qq.com>
Date: Fri, 11 Apr 2025 09:28:21 +0800
From: Yaxiong Tian <iambestgod@...com>
To: rafael@...nel.org,
	lukasz.luba@....com
Cc: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yaxiong Tian <tianyaxiong@...inos.cn>
Subject: [PATCH v2] PM: EM: Fix potential division-by-zero error in em_compute_costs()

From: Yaxiong Tian <tianyaxiong@...inos.cn>

When the device is of a non-CPU type, table[i].performance won't be
initialized in the previous em_init_performance(), resulting in division
by zero when calculating costs in em_compute_costs().

Since the 'cost' algorithm is only used for EAS energy efficiency
calculations and is currently not utilized by other device drivers, we
should add the _is_cpu_device(dev) check to prevent this division-by-zero
issue.

Fixes: <1b600da51073> ("PM: EM: Optimize em_cpu_energy() and remove division")
Signed-off-by: Yaxiong Tian <tianyaxiong@...inos.cn>
---
 kernel/power/energy_model.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index d9b7e2b38c7a..d1fa7e8787b5 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -244,7 +244,7 @@ static int em_compute_costs(struct device *dev, struct em_perf_state *table,
 					cost, ret);
 				return -EINVAL;
 			}
-		} else {
+		} else if (_is_cpu_device(dev)) {
 			/* increase resolution of 'cost' precision */
 			power_res = table[i].power * 10;
 			cost = power_res / table[i].performance;
-- 
2.25.1