On Thu, Dec 01, 2016 at 11:07:21AM +0100, Thomas Gleixner wrote:
> Yes, that makes a lot of sense.

Here it is:

---
From: Borislav Petkov <b...@suse.de>
Date: Thu, 1 Dec 2016 12:11:37 +0100
Subject: [PATCH] x86/CPU: Add X86_FEATURE_CPUID

Add a synthetic CPUID flag denoting whether the CPU sports the CPUID
instruction or not. This will come useful later when accomodating
CPUID-less CPUs.

Signed-off-by: Borislav Petkov <b...@suse.de>
---
 arch/x86/include/asm/cpufeatures.h | 2 +-
 arch/x86/kernel/cpu/common.c       | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h 
b/arch/x86/include/asm/cpufeatures.h
index 53e27a12ceb6..cb49dd31c3b2 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -100,7 +100,7 @@
 #define X86_FEATURE_XTOPOLOGY  ( 3*32+22) /* cpu topology enum extensions */
 #define X86_FEATURE_TSC_RELIABLE ( 3*32+23) /* TSC is known to be reliable */
 #define X86_FEATURE_NONSTOP_TSC        ( 3*32+24) /* TSC does not stop in C 
states */
-/* free, was #define X86_FEATURE_CLFLUSH_MONITOR ( 3*32+25) * "" clflush reqd 
with monitor */
+#define X86_FEATURE_CPUID      ( 3*32+25) /* CPU has CPUID instruction itself 
*/
 #define X86_FEATURE_EXTD_APICID        ( 3*32+26) /* has extended APICID (8 
bits) */
 #define X86_FEATURE_AMD_DCM     ( 3*32+27) /* multi-node processor */
 #define X86_FEATURE_APERFMPERF ( 3*32+28) /* APERFMPERF */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 90c007447507..8dcdcdeec569 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -800,14 +800,12 @@ static void __init early_identify_cpu(struct cpuinfo_x86 
*c)
        memset(&c->x86_capability, 0, sizeof c->x86_capability);
        c->extended_cpuid_level = 0;
 
-       if (!have_cpuid_p())
-               identify_cpu_without_cpuid(c);
-
        /* cyrix could have cpuid enabled via c_identify()*/
        if (have_cpuid_p()) {
                cpu_detect(c);
                get_cpu_vendor(c);
                get_cpu_cap(c);
+               setup_force_cpu_cap(X86_FEATURE_CPUID);
 
                if (this_cpu->c_early_init)
                        this_cpu->c_early_init(c);
@@ -817,6 +815,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
                if (this_cpu->c_bsp_init)
                        this_cpu->c_bsp_init(c);
+        } else {
+               identify_cpu_without_cpuid(c);
+               setup_clear_cpu_cap(X86_FEATURE_CPUID);
        }
 
        setup_force_cpu_cap(X86_FEATURE_ALWAYS);
-- 
2.10.0

-- 
Regards/Gruss,
    Boris.

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