mwait-idle: add SKX support

SKX is similar to BDX

Signed-off-by: Len Brown <len.brown@intel.com>
[Linux commit: f9e71657c2c0a8f1c50884ab45794be2854e158e]
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -530,6 +530,28 @@ static struct cpuidle_state skl_cstates[
 	{}
 };
 
+static const struct cpuidle_state skx_cstates[] = {
+	{
+		.name = "C1-SKX",
+		.flags = MWAIT2flg(0x00),
+		.exit_latency = 2,
+		.target_residency = 2,
+	},
+	{
+		.name = "C1E-SKX",
+		.flags = MWAIT2flg(0x01),
+		.exit_latency = 10,
+		.target_residency = 20,
+	},
+	{
+		.name = "C6-SKX",
+		.flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
+		.exit_latency = 133,
+		.target_residency = 600,
+	},
+	{}
+};
+
 static const struct cpuidle_state atom_cstates[] = {
 	{
 		.name = "C1E-ATM",
@@ -757,6 +779,11 @@ static const struct idle_cpu idle_cpu_sk
 	.disable_promotion_to_c1e = 1,
 };
 
+static const struct idle_cpu idle_cpu_skx = {
+	.state_table = skx_cstates,
+	.disable_promotion_to_c1e = 1,
+};
+
 static const struct idle_cpu idle_cpu_avn = {
 	.state_table = avn_cstates,
 	.disable_promotion_to_c1e = 1,
@@ -798,6 +825,7 @@ static const struct x86_cpu_id intel_idl
 	ICPU(0x56, bdw),
 	ICPU(0x4e, skl),
 	ICPU(0x5e, skl),
+	ICPU(0x55, skx),
 	ICPU(0x57, knl),
 	{}
 };