linux-kernel - [PATCH v3] x86/cpu: Add INTEL_LUNARLAKE_M to X86_BUG

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Message-ID: <a4aa8842a3c3bfdb7fe9807710eef159cbf0e705.1731463305.git.len.brown@intel.com>
Date: Tue, 12 Nov 2024 21:07:00 -0500
From: Len Brown <lenb@...nel.org>
To: peterz@...radead.org,
	tglx@...utronix.de,
	x86@...nel.org
Cc: rafael@...nel.org,
	linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Len Brown <len.brown@...el.com>,
	stable@...r.kernel.org
Subject: [PATCH v3] x86/cpu: Add INTEL_LUNARLAKE_M to X86_BUG_MONITOR

From: Len Brown <len.brown@...el.com>

Under some conditions, MONITOR wakeups on Lunar Lake processors
can be lost, resulting in significant user-visible delays.

Add LunarLake to X86_BUG_MONITOR so that wake_up_idle_cpu()
always sends an IPI, avoiding this potential delay.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219364

Cc: stable@...r.kernel.org # 6.11
Signed-off-by: Len Brown <len.brown@...el.com>
---
v3 syntax tweak
v2 leave smp_kick_mwait_play_dead() alone

 arch/x86/kernel/cpu/intel.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index e7656cbef68d..4b5f3d052151 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -586,7 +586,9 @@ static void init_intel(struct cpuinfo_x86 *c)
 	     c->x86_vfm == INTEL_WESTMERE_EX))
 		set_cpu_bug(c, X86_BUG_CLFLUSH_MONITOR);
 
-	if (boot_cpu_has(X86_FEATURE_MWAIT) && c->x86_vfm == INTEL_ATOM_GOLDMONT)
+	if (boot_cpu_has(X86_FEATURE_MWAIT) &&
+	    (c->x86_vfm == INTEL_ATOM_GOLDMONT ||
+	     c->x86_vfm == INTEL_LUNARLAKE_M))
 		set_cpu_bug(c, X86_BUG_MONITOR);
 
 #ifdef CONFIG_X86_64
-- 
2.43.0