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x86/cpu: Add Lunar Lake to list of CPUs with a broken MONITOR implementation
Under some conditions, MONITOR wakeups on Lunar Lake processors can be lost, resulting in significant user-visible delays. Add Lunar Lake to X86_BUG_MONITOR so that wake_up_idle_cpu() always sends an IPI, avoiding this potential delay. Reported originally here: https://bugzilla.kernel.org/show_bug.cgi?id=219364 [ dhansen: tweak subject ] Signed-off-by: Len Brown <[email protected]> Signed-off-by: Dave Hansen <[email protected]> Reviewed-by: Rafael J. Wysocki <[email protected]> Cc:[email protected] Link: https://lore.kernel.org/all/a4aa8842a3c3bfdb7fe9807710eef159cbf0e705.1731463305.git.len.brown%40intel.com
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arch/x86/kernel/cpu/intel.c

Lines changed: 3 additions & 1 deletion
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@@ -555,7 +555,9 @@ static void init_intel(struct cpuinfo_x86 *c)
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c->x86_vfm == INTEL_WESTMERE_EX))
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set_cpu_bug(c, X86_BUG_CLFLUSH_MONITOR);
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if (boot_cpu_has(X86_FEATURE_MWAIT) && c->x86_vfm == INTEL_ATOM_GOLDMONT)
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if (boot_cpu_has(X86_FEATURE_MWAIT) &&
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(c->x86_vfm == INTEL_ATOM_GOLDMONT ||
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c->x86_vfm == INTEL_LUNARLAKE_M))
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set_cpu_bug(c, X86_BUG_MONITOR);
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#ifdef CONFIG_X86_64

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