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Date:   Wed, 25 Jan 2017 03:41:26 -0800
From:   tip-bot for Andy Lutomirski <>
Subject: [tip:x86/fpu] x86/cpu: Re-apply forced caps every time CPU caps are

Commit-ID:  60d3450167433f2d099ce2869dc52dd9e7dc9b29
Author:     Andy Lutomirski <>
AuthorDate: Wed, 18 Jan 2017 11:15:39 -0800
Committer:  Ingo Molnar <>
CommitDate: Wed, 25 Jan 2017 10:12:41 +0100

x86/cpu: Re-apply forced caps every time CPU caps are re-read

Calling get_cpu_cap() will reset a bunch of CPU features.  This will
cause the system to lose track of force-set and force-cleared
features in the words that are reset until the end of CPU
initialization.  This can cause X86_FEATURE_FPU, for example, to
change back and forth during boot and potentially confuse CPU setup.

To minimize the chance of confusion, re-apply forced caps every time
get_cpu_cap() is called.

Signed-off-by: Andy Lutomirski <>
Reviewed-by: Borislav Petkov <>
Cc: Borislav Petkov <>
Cc: Brian Gerst <>
Cc: Dave Hansen <>
Cc: Fenghua Yu <>
Cc: H. Peter Anvin <>
Cc: Linus Torvalds <>
Cc: Matthew Whitehead <>
Cc: Oleg Nesterov <>
Cc: One Thousand Gnomes <>
Cc: Peter Zijlstra <>
Cc: Rik van Riel <>
Cc: Thomas Gleixner <>
Cc: Yu-cheng Yu <>
Signed-off-by: Ingo Molnar <>
 arch/x86/kernel/cpu/common.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 2ea16e0..d09b5ee 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -758,6 +758,13 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 		c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);
+	/*
+	 * Clear/Set all flags overridden by options, after probe.
+	 * This needs to happen each time we re-probe, which may happen
+	 * several times during CPU initialization.
+	 */
+	apply_forced_caps(c);
 static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)

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