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[v3] PM: EM: Fix potential division-by-zero error in em_compute_costs()

Message ID tencent_6D2374392DB66C9D23BF6E2546638A42EC08@qq.com
State New
Headers show
Series [v3] PM: EM: Fix potential division-by-zero error in em_compute_costs() | expand

Commit Message

Yaxiong Tian April 14, 2025, 9:04 a.m. UTC 
From: Yaxiong Tian <tianyaxiong@kylinos.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@kylinos.cn>
---
 kernel/power/energy_model.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index d9b7e2b38c7a..fc972cc1fc12 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -235,7 +235,7 @@  static int em_compute_costs(struct device *dev, struct em_perf_state *table,
 
 	/* Compute the cost of each performance state. */
 	for (i = nr_states - 1; i >= 0; i--) {
-		unsigned long power_res, cost;
+		unsigned long power_res, cost = 0;
 
 		if ((flags & EM_PERF_DOMAIN_ARTIFICIAL) && cb->get_cost) {
 			ret = cb->get_cost(dev, table[i].frequency, &cost);
@@ -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;