[tip:x86/urgent] x86/apic: Future-proof the TSC_DEADLINE quirk for SKX

[tip-bot for Len Brown]

Commit-ID:  d9e6dbcf28f383bf08e6a3180972f5722e514a54
Gitweb:     https://git.kernel.org/tip/d9e6dbcf28f383bf08e6a3180972f5722e514a54
Author:     Len Brown <len.brown@xxxxxxxxx>
AuthorDate: Sat, 21 Jul 2018 17:19:19 -0400
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 24 Jul 2018 10:05:13 +0200

x86/apic: Future-proof the TSC_DEADLINE quirk for SKX

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

Without this patch, upcoming SKX steppings will not be able to use
their TSC_DEADLINE timer.

Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx> # v4.14+
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: 616dd5872e ("x86/apic: Update TSC_DEADLINE quirk with additional SKX stepping")
Link: http://lkml.kernel.org/r/d0c7129e509660be9ec6b233284b8d42d90659e8.1532207856.git.len.brown@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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 2aabd4cb0e3f..adbda5847b14 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;
 }