x86/cpuidle: clean up statistics reporting to user mode

First of all, when no ACPI Cx data was reported, make sure the usage
count passed back to user mode is not random.

Besides that, fold a lot of redundant code.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 15 insertions, 30 deletions

diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index cf128a33e1..af19d0687d 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -1100,36 +1100,23 @@ int pmstat_get_cx_stat(uint32_t cpuid, struct pm_cx_stat *stat)
     }
 
     stat->last = power->last_state ? power->last_state->idx : 0;
-    stat->nr = power->count;
     stat->idle_time = get_cpu_idle_time(cpuid);
 
     /* mimic the stat when detail info hasn't been registered by dom0 */
     if ( pm_idle_save == NULL )
     {
-        /* C1 */
-        usage[1] = 1;
-        res[1] = stat->idle_time;
+        stat->nr = 2;
 
-        /* C0 */
-        res[0] = NOW() - res[1];
+        usage[1] = idle_usage = 1;
+        res[1] = idle_res = stat->idle_time;
 
-        if ( copy_to_guest_offset(stat->triggers, 0, &usage[0], 2) ||
-            copy_to_guest_offset(stat->residencies, 0, &res[0], 2) )
-            return -EFAULT;
-
-        stat->pc2 = 0;
-        stat->pc3 = 0;
-        stat->pc6 = 0;
-        stat->pc7 = 0;
-        stat->cc3 = 0;
-        stat->cc6 = 0;
-        stat->cc7 = 0;
-        return 0;
+        memset(&hw_res, 0, sizeof(hw_res));
     }
-
-    for ( i = power->count - 1; i >= 0; i-- )
+    else
     {
-        if ( i != 0 )
+        stat->nr = power->count;
+
+        for ( i = 1; i < power->count; i++ )
         {
             spin_lock_irq(&power->stat_lock);
             usage[i] = power->states[i].usage;
@@ -1139,18 +1126,16 @@ int pmstat_get_cx_stat(uint32_t cpuid, struct pm_cx_stat *stat)
             idle_usage += usage[i];
             idle_res += res[i];
         }
-        else
-        {
-            usage[i] = idle_usage;
-            res[i] = NOW() - idle_res;
-        }
+
+        get_hw_residencies(cpuid, &hw_res);
     }
 
-    if ( copy_to_guest_offset(stat->triggers, 0, &usage[0], power->count) ||
-        copy_to_guest_offset(stat->residencies, 0, &res[0], power->count) )
-        return -EFAULT;
+    usage[0] = idle_usage;
+    res[0] = NOW() - idle_res;
 
-    get_hw_residencies(cpuid, &hw_res);
+    if ( copy_to_guest(stat->triggers, usage, stat->nr) ||
+         copy_to_guest(stat->residencies, res, stat->nr) )
+        return -EFAULT;
 
     stat->pc2 = hw_res.pc2;
     stat->pc3 = hw_res.pc3;