intel_idle: Fix SPR C6 optimization

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 problematic 'return' statement. Fixes: 3a9cf77 ("intel_idle: add core C6 optimization for SPR") Suggested-by: Jan Beulich <[email protected]> Reported-by: Jan Beulich <[email protected]> Signed-off-by: Artem Bityutskiy <[email protected]> [ rjw: Minor changelog edits ] Signed-off-by: Rafael J. Wysocki <[email protected]>
chewitt · Apr 27, 2022 · 7eac3bd · 7eac3bd
1 parent 39c184a
commit 7eac3bd
Showing 1 changed file with 3 additions and 5 deletions.
diff --git 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;