[PATCH 2/3] x86/kernel: Skip TSC test and error messages if already unstable

[mike.travis]

If the TSC has already been determined to be unstable, then checking
TSC ADJUST values is a waste of time and generates unnecessary error
messages (840 for a 16 socket Skylake 28/2 core/ht system).

Signed-off-by: Mike Travis <mike.travis@xxxxxxx>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@xxxxxxx>
Reviewed-by: Russ Anderson <russ.anderson@xxxxxxx>
---
 arch/x86/kernel/tsc_sync.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- linux.orig/arch/x86/kernel/tsc_sync.c
+++ linux/arch/x86/kernel/tsc_sync.c
@@ -38,6 +38,10 @@ void tsc_verify_tsc_adjust(bool resume)
 	if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))
 		return;
 
+	/* Skip unnecessary error messages if TSC already unstable */
+	if (check_tsc_unstable())
+		return;
+
 	/* Rate limit the MSR check */
 	if (!resume && time_before(jiffies, adj->nextcheck))
 		return;
@@ -61,6 +65,9 @@ void tsc_verify_tsc_adjust(bool resume)
 static void tsc_sanitize_first_cpu(struct tsc_adjust *cur, s64 bootval,
 				   unsigned int cpu, bool bootcpu)
 {
+	/* Skip unnecessary error messages if TSC already unstable */
+	if (check_tsc_unstable())
+		return;
 	/*
 	 * First online CPU in a package stores the boot value in the
 	 * adjustment value. This value might change later via the sync

--