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Groups > linux.kernel > #1536580

[RFC PATCH 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read

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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
featueres 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@kernel.org>
---
 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 347ae0a19380..24e1e4004d42 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);
 
 	init_scattered_cpuid_features(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)
-- 
2.9.3

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[RFC PATCH 0/6] CPUID and FPU fixes Andy Lutomirski <luto@kernel.org> - 2016-12-06 02:10 +0100
  [RFC PATCH 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected" message Andy Lutomirski <luto@kernel.org> - 2016-12-06 02:10 +0100
    Re: [RFC PATCH 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected"  message Borislav Petkov <bp@alien8.de> - 2016-12-06 10:30 +0100
      Re: [RFC PATCH 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected" message Andy Lutomirski <luto@amacapital.net> - 2016-12-06 19:10 +0100
        Re: [RFC PATCH 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected"  message Borislav Petkov <bp@alien8.de> - 2016-12-06 19:10 +0100
  [RFC PATCH 5/6] x86/fpu: Fix CPUID-less FPU detection Andy Lutomirski <luto@kernel.org> - 2016-12-06 02:10 +0100
    Re: [RFC PATCH 5/6] x86/fpu: Fix CPUID-less FPU detection Borislav Petkov <bp@alien8.de> - 2016-12-06 10:50 +0100
      Re: [RFC PATCH 5/6] x86/fpu: Fix CPUID-less FPU detection Andy Lutomirski <luto@amacapital.net> - 2016-12-06 19:00 +0100
        Re: [RFC PATCH 5/6] x86/fpu: Fix CPUID-less FPU detection Borislav Petkov <bp@alien8.de> - 2016-12-07 10:50 +0100
  [RFC PATCH 6/6] x86/fpu: Fix the "Giving up, no FPU found" test Andy Lutomirski <luto@kernel.org> - 2016-12-06 02:10 +0100
  [RFC PATCH 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read Andy Lutomirski <luto@kernel.org> - 2016-12-06 02:10 +0100
    Re: [RFC PATCH 3/6] x86/cpu: Re-apply forced caps every time cpu  caps are re-read Borislav Petkov <bp@alien8.de> - 2016-12-06 10:00 +0100
  [RFC PATCH 2/6] x86/cpu: Factor out application of forced cpu caps Andy Lutomirski <luto@kernel.org> - 2016-12-06 02:10 +0100
    Re: [RFC PATCH 2/6] x86/cpu: Factor out application of forced cpu  caps Borislav Petkov <bp@alien8.de> - 2016-12-06 09:40 +0100

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