mwait-idle: support for Intel Xeon Phi Processor x200 Product Family

Enables "Intel(R) Xeon Phi(TM) Processor x200 Product Family" support,
formerly code-named KNL. It is based on modified Intel Atom Silvermont
microarchitecture.

Signed-off-by: Dasaratharaman Chandramouli <dasaratharaman.chandramouli@xxxxxxxxx>
[micah.barany@xxxxxxxxx: adjusted values of residency and latency]
Signed-off-by: Micah Barany <micah.barany@xxxxxxxxx>
[Linux commit: 281baf7a702693deaa45c98ef0c5161006b48257]
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -574,6 +574,22 @@ static const struct cpuidle_state avn_cs
 	{}
 };
 
+static const struct cpuidle_state knl_cstates[] = {
+	{
+		.name = "C1-KNL",
+		.flags = MWAIT2flg(0x00),
+		.exit_latency = 1,
+		.target_residency = 2,
+	},
+	{
+		.name = "C6-KNL",
+		.flags = MWAIT2flg(0x10) | CPUIDLE_FLAG_TLB_FLUSHED,
+		.exit_latency = 120,
+		.target_residency = 500,
+	},
+	{}
+};
+
 static void mwait_idle(void)
 {
 	unsigned int cpu = smp_processor_id();
@@ -748,6 +764,10 @@ static const struct idle_cpu idle_cpu_av
 	.disable_promotion_to_c1e = 1,
 };
 
+static const struct idle_cpu idle_cpu_knl = {
+	.state_table = knl_cstates,
+};
+
 #define ICPU(model, cpu) \
     { X86_VENDOR_INTEL, 6, model, X86_FEATURE_MONITOR, \
         &idle_cpu_##cpu}
@@ -780,6 +800,7 @@ static const struct x86_cpu_id intel_idl
 	ICPU(0x56, bdw),
 	ICPU(0x4e, skl),
 	ICPU(0x5e, skl),
+	ICPU(0x57, knl),
 	{}
 };