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Subject[patch 27/60] x86/cpufeatures: Add X86_BUG_CPU_INSECURE
From: Thomas Gleixner <>

Many x86 CPUs leak information to user space due to missing isolation of
user space and kernel space page tables. There are many well documented
ways to exploit that.

The upcoming software migitation of isolating the user and kernel space
page tables needs a misfeature flag so code can be made runtime

Add two BUG bits: One which indicates that the CPU is affected and one that
the software migitation is enabled.

Assume for now that _ALL_ x86 CPUs are affected by this. Exceptions can be
made later.

Signed-off-by: Thomas Gleixner <>

arch/x86/include/asm/cpufeatures.h | 2 ++
arch/x86/kernel/cpu/common.c | 4 ++++
2 files changed, 6 insertions(+)

--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -340,5 +340,7 @@
#define X86_BUG_SWAPGS_FENCE X86_BUG(11) /* SWAPGS without input dep on GS */
#define X86_BUG_MONITOR X86_BUG(12) /* IPI required to wake up remote CPU */
#define X86_BUG_AMD_E400 X86_BUG(13) /* CPU is among the affected by Erratum 400 */
+#define X86_BUG_CPU_INSECURE X86_BUG(14) /* CPU is insecure and needs kernel page table isolation */
+#define X86_BUG_CPU_SECURE_MODE_KPTI X86_BUG(15) /* Kernel Page Table Isolation enabled*/

#endif /* _ASM_X86_CPUFEATURES_H */
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1016,6 +1016,10 @@ static void __init early_identify_cpu(st

+ /* Assume for now that ALL x86 CPUs are insecure */
+ setup_force_cpu_bug(X86_BUG_CPU_INSECURE);

#ifdef CONFIG_X86_32

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