linux-kernel - [PATCH 1/1] x86/apic: Future-proof TSC

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Message-Id: <d0c7129e509660be9ec6b233284b8d42d90659e8.1532207856.git.len.brown@intel.com>
Date:   Sat, 21 Jul 2018 17:19:19 -0400
From:   Len Brown <lenb@...nel.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        Len Brown <len.brown@...el.com>
Subject: [PATCH 1/1] x86/apic: Future-proof TSC_DEADLINE quirk for SKX

From: Len Brown <len.brown@...el.com>

All SKX with stepping higher than 4 support the TSC_DEADLINE,
no matter the microcode version.

Fixes: 616dd5872e ("x86/apic: Update TSC_DEADLINE quirk with additional SKX stepping")

Signed-off-by: Len Brown <len.brown@...el.com>
---
Without this patch, upcoming SKX steppings will not be able to use
their TSC_DEADLINE timer.

 arch/x86/kernel/apic/apic.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index b203af0855b5..5caf8890fbe4 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -573,6 +573,9 @@ static u32 skx_deadline_rev(void)
 	case 0x04: return 0x02000014;
 	}
 
+	if (boot_cpu_data.x86_stepping > 4)
+		return 0;
+
 	return ~0U;
 }
 
-- 
2.18.0-rc0