x86: c1e_idle: don't mark TSC unstable if CPU has invariant TSC

Impact: Functional TSC is marked unstable on AMD family 0x10 and 0x11 CPUs.

This would be wrong because for those CPUs "invariant TSC" means:

   "The TSC counts at the same rate in all P-states, all C states, S0,
   or S1"

(See "Processor BIOS and Kernel Developer's Guides" for those CPUs.)

[ tglx: Changed C1E to AMD C1E in the printks to avoid confusion
	with Intel C1E ]

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index d8c2a29..876e918 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -270,8 +270,9 @@ static void c1e_idle(void)
                rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
                if (lo & K8_INTP_C1E_ACTIVE_MASK) {
                        c1e_detected = 1;
-                       mark_tsc_unstable("TSC halt in C1E");
-                       printk(KERN_INFO "System has C1E enabled\n");
+                       if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
+                               mark_tsc_unstable("TSC halt in AMD C1E");
+                       printk(KERN_INFO "System has AMD C1E enabled\n");
                        set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
                }
        }