diff mbox series

[2/2] intel_idle: fix SPR C6 optimization

Message ID 20220427060853.3975453-3-dedekind1@gmail.com
State New
Headers show
Series intel_idle fixes for 5.18 | expand

Commit Message

Artem Bityutskiy April 27, 2022, 6:08 a.m. UTC 
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

This patch is a fix for the following 5.18-rc1 commit:
	commit 3a9cf77b60dc intel_idle: add core C6 optimization for SPR

The Sapphire Rapids (SPR) C6 optimization was added to the end of the
'spr_idle_state_table_update()' function. However, the function has a
'return' which may happen before the optimization has a chance to run.
And this may prevent the optimization from happening.

This is an unlikely scenario, but possible if user boots with, say,
the 'intel_idle.preferred_cstates=6' kernel boot option.

This patch fixes the issue by eliminating the 'return'.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
 drivers/idle/intel_idle.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index cf5ed4c1d02c..ae8649a809ea 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1581,11 +1581,9 @@  static void __init spr_idle_state_table_update(void)
 	unsigned long long msr;
 
 	/* Check if user prefers C1E over C1. */
-	if (preferred_states_mask & BIT(2)) {
-		if (preferred_states_mask & BIT(1))
-			/* Both can't be enabled, stick to the defaults. */
-			return;
-
+	if ((preferred_states_mask & BIT(2)) &&
+	    !(preferred_states_mask & BIT(1))) {
+		/* Disable C1 and enable C1E. */
 		spr_cstates[0].flags |= CPUIDLE_FLAG_UNUSABLE;
 		spr_cstates[1].flags &= ~CPUIDLE_FLAG_UNUSABLE;