x86/tsc: Use X86_FEATURE_TSC_ADJUST in detect_art()

The art detection uses rdmsrl_safe() to detect the availablity of the
TSC_ADJUST MSR.

That's pointless because we have a feature bit for this. Use it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.483561692@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 8 insertions, 6 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 0ff1ec61d1e4..2b27c5ae9d1f 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1057,18 +1057,20 @@ static void detect_art(void)
         if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
                 return;
 
-        cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
-              &art_to_tsc_numerator, unused, unused+1);
-
-        /* Don't enable ART in a VM, non-stop TSC required */
+        /* Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required */
         if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
             !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
-            art_to_tsc_denominator < ART_MIN_DENOMINATOR)
+            !boot_cpu_has(X86_FEATURE_TSC_ADJUST))
                 return;
 
-        if (rdmsrl_safe(MSR_IA32_TSC_ADJUST, &art_to_tsc_offset))
+        cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
+              &art_to_tsc_numerator, unused, unused+1);
+
+        if (art_to_tsc_denominator < ART_MIN_DENOMINATOR)
                 return;
 
+        rdmsrl(MSR_IA32_TSC_ADJUST, art_to_tsc_offset);
+
         /* Make this sticky over multiple CPU init calls */
         setup_force_cpu_cap(X86_FEATURE_ART);
 }