x86, AMD: Set ARAT feature on AMD processors

commit b87cf80a upstream.

Support for Always Running APIC timer (ARAT) was introduced in
commit db954b58

. This feature
allows us to avoid switching timers from LAPIC to something else
(e.g. HPET) and go into timer broadcasts when entering deep
C-states.

AMD processors don't provide a CPUID bit for that feature but
they also keep APIC timers running in deep C-states (except for
cases when the processor is affected by erratum 400). Therefore
we should set ARAT feature bit on AMD CPUs.
Tested-by: Borislav Petkov <borislav.petkov@amd.com>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Mark Langsdorf <mark.langsdorf@amd.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@amd.com>
LKML-Reference: <1300205624-4813-1-git-send-email-ostr@amd64.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/x86/kernel/cpu/amd.c

@@ -566,6 +566,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 		}
 	}
 #endif
+
+	/* As a rule processors have APIC timer running in deep C states */
+	if (c->x86 >= 0xf && !cpu_has_amd_erratum(amd_erratum_400))
+		set_cpu_cap(c, X86_FEATURE_ARAT);
 }
 
 #ifdef CONFIG_X86_32