linux-kernel - [tip:x86/apic] x86/apic: Silence "FW_BUG TSC_DEADLINE disabled due to Errata" on CPUs without the feature

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Message-ID: <tip-594a30fb12424717a41c62323d2a8bf167dbccad@git.kernel.org>
Date:   Thu, 31 Aug 2017 02:55:50 -0700
From:   tip-bot for Hans de Goede <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, hdegoede@...hat.com, hpa@...or.com,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        frank.mehnert@...cle.com, peterz@...radead.org, mingo@...nel.org,
        michael.thayer@...cle.com, michal.necasek@...cle.com
Subject: [tip:x86/apic] x86/apic: Silence "FW_BUG TSC_DEADLINE disabled due
 to Errata" on CPUs without the feature

Commit-ID:  594a30fb12424717a41c62323d2a8bf167dbccad
Gitweb:     http://git.kernel.org/tip/594a30fb12424717a41c62323d2a8bf167dbccad
Author:     Hans de Goede <hdegoede@...hat.com>
AuthorDate: Wed, 30 Aug 2017 12:58:11 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 31 Aug 2017 11:17:27 +0200

x86/apic: Silence "FW_BUG TSC_DEADLINE disabled due to Errata" on CPUs without the feature

When booting 4.13 on a VirtualBox VM on a Skylake host the following
error shows up in the logs:

 [    0.000000] [Firmware Bug]: TSC_DEADLINE disabled due to Errata;
                please update microcode to version: 0xb2 (or later)

This is caused by apic_check_deadline_errata() only checking CPU model
and not the X86_FEATURE_TSC_DEADLINE_TIMER flag (which VirtualBox does
NOT export to the guest), combined with VirtualBox not exporting the
micro-code version to the guest.

This commit adds a check for X86_FEATURE_TSC_DEADLINE_TIMER to
apic_check_deadline_errata(), silencing this error on VirtualBox VMs.

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Frank Mehnert <frank.mehnert@...cle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael Thayer <michael.thayer@...cle.com>
Cc: Michal Necasek <michal.necasek@...cle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Fixes: bd9240a18e ("x86/apic: Add TSC_DEADLINE quirk due to errata")
Link: http://lkml.kernel.org/r/20170830105811.27539-1-hdegoede@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/apic/apic.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index eebee4c..7834f73 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -597,9 +597,13 @@ static const struct x86_cpu_id deadline_match[] = {
 
 static void apic_check_deadline_errata(void)
 {
-	const struct x86_cpu_id *m = x86_match_cpu(deadline_match);
+	const struct x86_cpu_id *m;
 	u32 rev;
 
+	if (!boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER))
+		return;
+
+	m = x86_match_cpu(deadline_match);
 	if (!m)
 		return;