[PATCH 4.4 099/107] x86/cpu: Re-apply forced caps every time CPU caps are re-read
From: Greg Kroah-Hartman
Date: Mon Jul 23 2018 - 08:47:12 EST
4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Andy Lutomirski <luto@xxxxxxxxxx>
commit 60d3450167433f2d099ce2869dc52dd9e7dc9b29 upstream.
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 <luto@xxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matthew Whitehead <tedheadster@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Link: http://lkml.kernel.org/r/c817eb373d2c67c2c81413a70fc9b845fa34a37e.1484705016.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Srivatsa S. Bhat <srivatsa@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/common.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -803,6 +803,13 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
init_scattered_cpuid_features(c);
init_speculation_control(c);
+
+ /*
+ * 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)