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Subject[PATCH v2 2/2] x86/cpu: Change query logic so cpuid is enabled before testing
Date
Presently we check for cpuid to be enabled first. If it is not already
enabled, then we next call identify_cpu_without_cpuid() and clear
X86_FEATURE_CPUID.

Unfortunately, identify_cpu_without_cpuid() is the function where cpuid
becomes _enabled_ on Cyrix 6x86/6x86L cpus. So we must reverse the
calling sequence so that cpuid is first enabled, and then check a second
time to see if the feature has now been activated.

Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Matthew Whitehead <tedheadster@gmail.com>
---
arch/x86/kernel/cpu/common.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index eb4cb3efd20e..60c7c5ce7e55 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1040,6 +1040,9 @@ 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);
@@ -1057,7 +1060,6 @@ 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);
}

--
2.16.4
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