[PATCH] xen/sched: fix get_cpu_idle_time() for smt=0 suspend/resume

[Juergen Gross <jgross@xxxxxxxx>]

With smt=0 during a suspend/resume cycle of the machine the threads
which have been parked before will briefly come up again. This can
result in problems e.g. with cpufreq driver being active as this will
call into get_cpu_idle_time() for a cpu without initialized scheduler
data.

Fix that by letting get_cpu_idle_time() deal with this case.

Fixes: 132cbe8f35632fb2 ("sched: fix get_cpu_idle_time() with core scheduling")
Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Tested-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
An alternative way to fix the issue would be to keep the sched_resource
of offline cpus allocated like we already do with idle vcpus and units.
This fix would be more intrusive, but it would avoid similar other bugs
like this one.
---
 xen/common/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 6d34764d38..9ac1b01ca8 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -337,7 +337,7 @@ uint64_t get_cpu_idle_time(unsigned int cpu)
     struct vcpu_runstate_info state = { 0 };
     const struct vcpu *v = idle_vcpu[cpu];
 
-    if ( cpu_online(cpu) && v )
+    if ( cpu_online(cpu) && v && get_sched_res(cpu) )
         vcpu_runstate_get(v, &state);
 
     return state.time[RUNSTATE_running];
-- 
2.26.2