[patch 1/8] x86/tsc: Use X86_FEATURE_TSC_ADJUST in detect_art()

[Thomas Gleixner]

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@xxxxxxxxxxxxx>
---
 arch/x86/kernel/tsc.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1043,18 +1043,20 @@ 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);
 }