Up to now reading the stolen time of a remote cpu was not possible in a
performant way under Xen. This made support of runqueue steal time via
paravirt_steal_rq_enabled impossible.
With the addition of an appropriate hypervisor interface this is now
possible, so add the support.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
-/*
- * Runstate accounting
- */
-void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
+static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
+ unsigned int cpu)
{
u64 state_time;
struct vcpu_runstate_info *state;
BUG_ON(preemptible());
{
u64 state_time;
struct vcpu_runstate_info *state;
BUG_ON(preemptible());
- state = this_cpu_ptr(&xen_runstate);
+ state = per_cpu_ptr(&xen_runstate, cpu);
- /*
- * The runstate info is always updated by the hypervisor on
- * the current CPU, so there's no need to use anything
- * stronger than a compiler barrier when fetching it.
- */
do {
state_time = get64(&state->state_entry_time);
do {
state_time = get64(&state->state_entry_time);
+ rmb(); /* Hypervisor might update data. */
*res = READ_ONCE(*state);
*res = READ_ONCE(*state);
- } while (get64(&state->state_entry_time) != state_time);
+ rmb(); /* Hypervisor might update data. */
+ } while (get64(&state->state_entry_time) != state_time ||
+ (state_time & XEN_RUNSTATE_UPDATE));
+}
+
+/*
+ * Runstate accounting
+ */
+void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
+{
+ xen_get_runstate_snapshot_cpu(res, smp_processor_id());
}
/* return true when a vcpu could run but has no real cpu to run on */
}
/* return true when a vcpu could run but has no real cpu to run on */
{
struct vcpu_runstate_info state;
{
struct vcpu_runstate_info state;
- BUG_ON(cpu != smp_processor_id());
- xen_get_runstate_snapshot(&state);
+ xen_get_runstate_snapshot_cpu(&state, cpu);
return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
}
return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
}
void __init xen_time_setup_guest(void)
{
void __init xen_time_setup_guest(void)
{
+ bool xen_runstate_remote;
+
+ xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
+ VMASST_TYPE_runstate_update_flag);
+
pv_time_ops.steal_clock = xen_steal_clock;
static_key_slow_inc(¶virt_steal_enabled);
pv_time_ops.steal_clock = xen_steal_clock;
static_key_slow_inc(¶virt_steal_enabled);
- /*
- * We can't set paravirt_steal_rq_enabled as this would require the
- * capability to read another cpu's runstate info.
- */
+ if (xen_runstate_remote)
+ static_key_slow_inc(¶virt_steal_rq_enabled);