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Commit 7b3d2f6e authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarIngo 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: default avatarThomas Gleixner <tglx@linutronix.de>
parent 984feceb

arch/x86/kernel/tsc.c

+8 −6
Original line number Diff line number Diff line
@@ -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);

}