[Xen-devel] [PATCH v3 1/3] x86: Allow limiting the max C-state sub-state

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

Allow limiting the max C-state sub-state by appending to the max_cstate
command-line parameter. E.g. max_cstate=1,0
The limit only applies to the highest legal C-state. For example:
 max_cstate = 1, max_csubstate = 0 ==> C0, C1 okay, but not C1E
 max_cstate = 1, max_csubstate = 1 ==> C0, C1 and C1E okay, but not C2
 max_cstate = 2, max_csubstate = 0 ==> C0, C1, C1E, C2 okay, but not C3
 max_cstate = 2, max_csubstate = 1 ==> C0, C1, C1E, C2 okay, but not C3

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
CC: Liu Jinsong <jinsong.liu@xxxxxxxxxxxxxxx>
---
 docs/misc/xen-command-line.markdown |  8 +++++++-
 xen/arch/x86/acpi/cpu_idle.c        | 21 ++++++++++++++++++---
 xen/arch/x86/cpu/mwait-idle.c       |  4 +++-
 xen/include/xen/acpi.h              | 16 ++++++++++++----
 4 files changed, 40 insertions(+), 9 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 94f04bd..f4f4109 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -715,7 +715,13 @@ so the crash kernel may find find them.  Should be used in 
combination
 with **crashinfo_maxaddr**.
 
 ### max\_cstate
-> `= <integer>`
+> `= <cstate>[,<substate>]`
+
+`cstate` is an integer which limits the maximum C-state that Xen uses.
+
+`substate` is an integer which limits the maximum sub C-state that Xen
+uses.  The limit only applies to the highest legal C-state.
+
 
 ### max\_gsi\_irqs
 > `= <integer>`
diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index b05fb39..9cb5076 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -105,7 +105,16 @@ static uint64_t (*__read_mostly tick_to_ns)(uint64_t) = 
acpi_pm_tick_to_ns;
 
 void (*__read_mostly pm_idle_save)(void);
 unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER - 1;
-integer_param("max_cstate", max_cstate);
+unsigned int max_csubstate __read_mostly = UINT_MAX;
+
+static void __init parse_cstate(const char *s)
+{
+    max_cstate = simple_strtoul(s, &s, 0);
+    if ( *s == ',' )
+        max_csubstate = simple_strtoul(s + 1, &s, 0);
+}
+custom_param("max_cstate", parse_cstate);
+
 static bool_t __read_mostly local_apic_timer_c2_ok;
 boolean_param("lapic_timer_c2_ok", local_apic_timer_c2_ok);
 
@@ -240,6 +249,7 @@ static void print_acpi_power(uint32_t cpu, struct 
acpi_processor_power *power)
     last_state_idx = power->last_state ? power->last_state->idx : -1;
     printk("active state:\t\tC%d\n", last_state_idx);
     printk("max_cstate:\t\tC%d\n", max_cstate);
+    printk("max_csubstate:\t\t%u\n", max_csubstate);
     printk("states:\n");
     
     for ( i = 1; i < power->count; i++ )
@@ -484,8 +494,13 @@ static void acpi_processor_idle(void)
         if ( cx->type == ACPI_STATE_C3 && power->flags.bm_check &&
              acpi_idle_bm_check() )
             cx = power->safe_state;
-        if ( cx->idx > max_cstate )
-            cx = &power->states[max_cstate];
+        while ( (cx->type > max_cstate ||
+                 cx->entry_method == ACPI_CSTATE_EM_NONE ||
+                 (cx->entry_method == ACPI_CSTATE_EM_FFH &&
+                   cx->type == max_cstate &&
+                   (cx->address & MWAIT_SUBSTATE_MASK) > max_csubstate)) &&
+               next_state-- )
+            cx = &power->states[next_state];
         menu_get_trace_data(&exp, &pred);
     }
     if ( !cx )
diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index 38172e5..3bad6d8 100644
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -330,7 +330,9 @@ static void mwait_idle(void)
            (next_state = cpuidle_current_governor->select(power)) > 0) {
                do {
                        cx = &power->states[next_state];
-               } while (cx->type > max_cstate && --next_state);
+               } while ((cx->type > max_cstate || (cx->type == max_cstate &&
+                         MWAIT_HINT2SUBSTATE(cx->address) > max_csubstate)) &&
+                        --next_state);
                if (!next_state)
                        cx = NULL;
                menu_get_trace_data(&exp, &pred);
diff --git a/xen/include/xen/acpi.h b/xen/include/xen/acpi.h
index 3aeba4a..331dc8d 100644
--- a/xen/include/xen/acpi.h
+++ b/xen/include/xen/acpi.h
@@ -124,13 +124,21 @@ void acpi_unregister_gsi (u32 gsi);
 
 #ifdef CONFIG_ACPI_CSTATE
 /*
- * Set highest legal C-state
- * 0: C0 okay, but not C1
- * 1: C1 okay, but not C2
- * 2: C2 okay, but not C3 etc.
+ * max_cstate sets the highest legal C-state.
+ * max_cstate = 0: C0 okay, but not C1
+ * max_cstate = 1: C1 okay, but not C2
+ * max_cstate = 2: C2 okay, but not C3 etc.
+
+ * max_csubstate sets the highest legal C-state sub-state. Only applies to the
+ * highest legal C-state.
+ * max_cstate = 1, max_csubstate = 0 ==> C0, C1 okay, but not C1E
+ * max_cstate = 1, max_csubstate = 1 ==> C0, C1 and C1E okay, but not C2
+ * max_cstate = 2, max_csubstate = 0 ==> C0, C1, C1E, C2 okay, but not C3
+ * max_cstate = 2, max_csubstate = 1 ==> C0, C1, C1E, C2 okay, but not C3
  */
 
 extern unsigned int max_cstate;
+extern unsigned int max_csubstate;
 
 static inline unsigned int acpi_get_cstate_limit(void)
 {
-- 
1.9.3


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