x86/smpboot: Make optimization of delay calibration work correctly

If the TSC has constant frequency then the delay calibration can be skipped
when it has been calibrated for a package already. This is checked in
calibrate_delay_is_known(), but that function is buggy in two aspects:

It returns 'false' if

  (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC)

which is obviously the reverse of the intended check and the check for the
sibling mask cannot work either because the topology links have not been
set up yet.

Correct the condition and move the call to set_cpu_sibling_map() before
invoking calibrate_delay() so the sibling check works correctly.

[ tglx: Rewrote changelong ]

Fixes: c25323c07345 ("x86/tsc: Use topology functions")
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: bob.picco@oracle.com
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20171028001100.26603-1-pasha.tatashin@oracle.com

2 files changed, 9 insertions, 10 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ad59edd84de7..65a0ccdc3050 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -194,6 +194,12 @@ static void smp_callin(void)
 	smp_store_cpu_info(cpuid);
 
 	/*
+	 * The topology information must be up to date before
+	 * calibrate_delay() and notify_cpu_starting().
+	 */
+	set_cpu_sibling_map(raw_smp_processor_id());
+
+	/*
 	 * Get our bogomips.
 	 * Update loops_per_jiffy in cpu_data. Previous call to
 	 * smp_store_cpu_info() stored a value that is close but not as
@@ -203,11 +209,6 @@ static void smp_callin(void)
 	cpu_data(cpuid).loops_per_jiffy = loops_per_jiffy;
 	pr_debug("Stack at about %p\n", &cpuid);
 
-	/*
-	 * This must be done before setting cpu_online_mask
-	 * or calling notify_cpu_starting.
-	 */
-	set_cpu_sibling_map(raw_smp_processor_id());
 	wmb();
 
 	notify_cpu_starting(cpuid);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 796d96bb0821..ad2b925a808e 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1346,12 +1346,10 @@ void __init tsc_init(void)
 unsigned long calibrate_delay_is_known(void)
 {
 	int sibling, cpu = smp_processor_id();
-	struct cpumask *mask = topology_core_cpumask(cpu);
+	int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC);
+	const struct cpumask *mask = topology_core_cpumask(cpu);
 
-	if (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC))
-		return 0;
-
-	if (!mask)
+	if (tsc_disabled || !constant_tsc || !mask)
 		return 0;
 
 	sibling = cpumask_any_but(mask, cpu);