linux-kernel - [PATCH] Revert "intel_idle: Rescan "dead" SMT siblings during, initialization"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <724616a2-6374-4ba3-8ce3-ea9c45e2ae3b@arm.com>
Date: Thu, 28 Aug 2025 15:25:58 +0100
From: Christian Loehle <christian.loehle@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 linux-pm <linux-pm@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Subject: [PATCH] Revert "intel_idle: Rescan "dead" SMT siblings during,
 initialization"

This reverts commit a430c11f401589a0f4f57fd398271a5d85142c7a.

Calling arch_cpu_rescan_dead_smt_siblings() in intel_idle_init with
boot parameter nosmt and maxcpus active hotplugged boot-offline CPUs
in (and leave them online) which weren't supposed to be online.

With the revert and nosmt and maxcpus=12 on a raptor lake:
cpu	online	capacity
cpu0	1	1009
cpu1	0	-
cpu2	1	1009
cpu3	0	-
cpu4	1	1009
cpu5	0	-
cpu6	1	1009
cpu7	0	-
cpu8	1	1024
cpu9	0	-
cpu10	1	1024
cpu11	0	-
cpu12	1	1009
cpu13	0	-
cpu14	1	1009
cpu15	0	-
cpu16	1	623
cpu17	1	623
cpu18	1	623
cpu19	1	623
cpu20	0	-
cpu21	0	-
cpu22	0	-
cpu23	0	-

Previously:
cpu	online	capacity
cpu0	1	1009
cpu1	0	-
cpu2	1	1009
cpu3	0	-
cpu4	1	1009
cpu5	0	-
cpu6	1	1009
cpu7	0	-
cpu8	1	1024
cpu9	0	-
cpu10	1	1024
cpu11	0	-
cpu12	1	1009
cpu13	0	-
cpu14	1	1009
cpu15	0	-
cpu16	1	623
cpu17	1	623
cpu18	1	623
cpu19	1	623
cpu20	1	623
cpu21	1	623
cpu22	1	623
cpu23	1	623

Signed-off-by: Christian Loehle <christian.loehle@....com>
---
Rafael, I don't immediately see how to fix this properly so I won't
try to, feel free to treat this as a bug report.

 drivers/idle/intel_idle.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 91a7b7e7c0c8..a9c58395a425 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -2507,8 +2507,6 @@ static int __init intel_idle_init(void)
 	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:
-- 
2.34.1