[PATCH 4.17 18/31] x86/apic: Future-proof the TSC_DEADLINE quirk for SKX

[Greg Kroah-Hartman]

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Len Brown <len.brown@xxxxxxxxx>

commit d9e6dbcf28f383bf08e6a3180972f5722e514a54 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- 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;
 }