[PATCH 2/2] x86/mwait-idle: Customize IceLake server support

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

From: Chen Yu <yu.c.chen@xxxxxxxxx>

On ICX platform, the C1E auto-promotion is enabled by default.
As a result, the CPU might fall into C1E more offen than previous
platforms. So disable C1E auto-promotion and expose C1E as a separate
idle state.

Beside C1 and C1E, the exit latency of C6 was measured
by a dedicated tool. However the exit latency(41us) exposed
by _CST is much smaller than the one we measured(128us). This
is probably due to the _CST uses the exit latency when woken
up from PC0+C6, rather than PC6+C6 when C6 was measured. Choose
the latter as we need the longest latency in theory.

Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
[Linux commit a472ad2bcea479ba068880125d7273fc95c14b70]
Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
---
Applying this gives almost 100% boost in sysbench cpu test on Whitley SDP
---
 xen/arch/x86/cpu/mwait-idle.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index 8add13d..f0c6ff9 100644
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -554,6 +554,28 @@ static const struct cpuidle_state skx_cstates[] = {
        {}
 };
 
+static const struct cpuidle_state icx_cstates[] = {
+       {
+               .name = "C1-ICX",
+               .flags = MWAIT2flg(0x00),
+               .exit_latency = 1,
+               .target_residency = 1,
+       },
+       {
+               .name = "C1E-ICX",
+               .flags = MWAIT2flg(0x01),
+               .exit_latency = 4,
+               .target_residency = 4,
+       },
+       {
+               .name = "C6-ICX",
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 128,
+               .target_residency = 384,
+       },
+       {}
+};
+
 static const struct cpuidle_state atom_cstates[] = {
        {
                .name = "C1E-ATM",
@@ -904,6 +926,11 @@ static const struct idle_cpu idle_cpu_skx = {
        .disable_promotion_to_c1e = 1,
 };
 
+static const struct idle_cpu idle_cpu_icx = {
+       .state_table = icx_cstates,
+       .disable_promotion_to_c1e = 1,
+};
+
 static const struct idle_cpu idle_cpu_avn = {
        .state_table = avn_cstates,
        .disable_promotion_to_c1e = 1,
@@ -958,6 +985,7 @@ static const struct x86_cpu_id intel_idle_ids[] 
__initconstrel = {
        ICPU(0x8e, skl),
        ICPU(0x9e, skl),
        ICPU(0x55, skx),
+       ICPU(0x6a, icx),
        ICPU(0x57, knl),
        ICPU(0x85, knl),
        ICPU(0x5c, bxt),
-- 
2.7.4