linux-kernel - [tip:x86/timers] x86/tsc: Drastically reduce the number of firmware bug warnings

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Message-ID: <tip-41e7864ab5ce4ec36e89a9f55d8d9dfe19b0392c@git.kernel.org>
Date:   Mon, 16 Oct 2017 14:16:46 -0700
From:   "tip-bot for mike.travis@....com" <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, bin.gao@...ux.intel.com,
        dimitri.sivanich@....com, andrew.banman@....com, mingo@...nel.org,
        mike.travis@....com, prarit@...hat.com, peterz@...radead.org,
        hpa@...or.com, russ.anderson@....com, linux-kernel@...r.kernel.org
Subject: [tip:x86/timers] x86/tsc: Drastically reduce the number of firmware
 bug warnings

Commit-ID:  41e7864ab5ce4ec36e89a9f55d8d9dfe19b0392c
Gitweb:     https://git.kernel.org/tip/41e7864ab5ce4ec36e89a9f55d8d9dfe19b0392c
Author:     mike.travis@....com <mike.travis@....com>
AuthorDate: Thu, 12 Oct 2017 11:32:04 -0500
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 16 Oct 2017 22:50:36 +0200

x86/tsc: Drastically reduce the number of firmware bug warnings

Prior to the TSC ADJUST MSR being available, the method to set TSC's in
sync with each other naturally caused a small skew between cpu threads.
This was NOT a firmware bug at the time so introducing a whole avalanche
of alarming warning messages might cause unnecessary concern and customer
complaints. (Example: >3000 msgs in a 32 socket Skylake system.)

Simply report the warning condition, if possible do the necessary fixes,
and move on.

Signed-off-by: Mike Travis <mike.travis@....com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@....com>
Reviewed-by: Russ Anderson <russ.anderson@....com>
Reviewed-by: Peter Zijlstra <peterz@...radead.org>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Andrew Banman <andrew.banman@....com>
Cc: Bin Gao <bin.gao@...ux.intel.com>
Link: https://lkml.kernel.org/r/20171012163202.175062400@stormcage.americas.sgi.com

---
 arch/x86/kernel/tsc_sync.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 3bdb983..26ba053 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -177,10 +177,9 @@ bool tsc_store_and_check_tsc_adjust(bool bootcpu)
 	 * Compare the boot value and complain if it differs in the
 	 * package.
 	 */
-	if (bootval != ref->bootval) {
-		pr_warn(FW_BUG "TSC ADJUST differs: Reference CPU%u: %lld CPU%u: %lld\n",
-			refcpu, ref->bootval, cpu, bootval);
-	}
+	if (bootval != ref->bootval)
+		printk_once(FW_BUG "TSC ADJUST differs within socket(s), fixing all errors\n");
+
 	/*
 	 * The TSC_ADJUST values in a package must be the same. If the boot
 	 * value on this newly upcoming CPU differs from the adjustment
@@ -188,8 +187,6 @@ bool tsc_store_and_check_tsc_adjust(bool bootcpu)
 	 * adjusted value.
 	 */
 	if (bootval != ref->adjusted) {
-		pr_warn("TSC ADJUST synchronize: Reference CPU%u: %lld CPU%u: %lld\n",
-			refcpu, ref->adjusted, cpu, bootval);
 		cur->adjusted = ref->adjusted;
 		wrmsrl(MSR_IA32_TSC_ADJUST, ref->adjusted);
 	}