linux-kernel - [PATCH v2] x86/apic: Silence "FW_BUG TSC_DEADLINE disabled due to Errata" on CPUs without the feature

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Message-Id: <20170830105811.27539-1-hdegoede@redhat.com>
Date:   Wed, 30 Aug 2017 12:58:11 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     Hans de Goede <hdegoede@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Necasek <michal.necasek@...cle.com>,
        Frank Mehnert <frank.mehnert@...cle.com>,
        Michael Thayer <michael.thayer@...cle.com>
Subject: [PATCH v2] 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.

Fixes: bd9240a18e ("x86/apic: Add TSC_DEADLINE quirk due to errata")
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Michal Necasek <michal.necasek@...cle.com>
Cc: Frank Mehnert <frank.mehnert@...cle.com>
Cc: Michael Thayer <michael.thayer@...cle.com>
Signed-off-by: Hans de Goede <hdegoede@...hat.com>
---
Changes in v2:
-Add an important missing "NOT" in a sentence in the commit message
---
 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 98b3dd8cf2bf..b3273c842850 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -599,9 +599,13 @@ 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;
 
-- 
2.13.4