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When booting a recent 32-bit i686 kernel on a multi-cpu system with 'pcid' cpu feature, only the boot cpu is correctly initialized. The other cpu's fail to initialize, resulting in a badly running or crashing kernel.

The reason is two missing patches present in vanilla upstream kernels:
x86/mm: Disable PCID on 32-bit kernels
x86/mm/32: Move setup_clear_cpu_cap(X86_FEATURE_PCID) earlier

Submitted-by: Jerome Borsboom
Applied-by: Akemi Yagi <>

--- a/arch/x86/kernel/cpu/common.c	2020-10-21 10:17:08.000000000 -0700
+++ b/arch/x86/kernel/cpu/common.c	2020-12-09 22:10:47.945329193 -0800
@@ -1131,6 +1131,14 @@ static void __init early_identify_cpu(st
+#ifdef CONFIG_X86_32
+	/*
+	* Regardless of whether PCID is enumerated, the SDM says
+	* that it can't be enabled in 32-bit mode.
+	*/
+	setup_clear_cpu_cap(X86_FEATURE_PCID);
 void __init early_cpu_init(void)