linux-kernel - [PATCH v1 3/5] intel_idle: Rescan "dead" SMT siblings during initialization

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Message-ID: <10669885.nUPlyArG6x@rjwysocki.net>
Date: Thu, 05 Jun 2025 17:06:08 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: x86 Maintainers <x86@...nel.org>, Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Linux ACPI <linux-acpi@...r.kernel.org>
Subject:
 [PATCH v1 3/5] intel_idle: Rescan "dead" SMT siblings during initialization

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Make intel_idle_init() call arch_cpu_rescan_dead_smt_siblings() after
successfully registering intel_idle as the cpuidle driver so as to
allow the "dead" SMT siblings (if any) to go into deep idle states.

This is necessary for the processor to be able to reach deep package
C-states (like PC10) going forward which is requisite for reducing
power sufficiently in suspend-to-idle, among other things.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/idle/intel_idle.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -2506,6 +2506,8 @@
 	pr_debug("Local APIC timer is reliable in %s\n",
 		 boot_cpu_has(X86_FEATURE_ARAT) ? "all C-states" : "C1");

+	arch_cpu_rescan_dead_smt_siblings();
+
 	return 0;

 hp_setup_fail: