xen: support runqueue steal time on xen
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>
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@ -47,27 +47,31 @@ static u64 get64(const u64 *p)
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return ret;
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}
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/*
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* Runstate accounting
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*/
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void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
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static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
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unsigned int cpu)
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{
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u64 state_time;
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struct vcpu_runstate_info *state;
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BUG_ON(preemptible());
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state = this_cpu_ptr(&xen_runstate);
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state = per_cpu_ptr(&xen_runstate, cpu);
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/*
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* The runstate info is always updated by the hypervisor on
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* the current CPU, so there's no need to use anything
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* stronger than a compiler barrier when fetching it.
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*/
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do {
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state_time = get64(&state->state_entry_time);
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rmb(); /* Hypervisor might update data. */
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*res = READ_ONCE(*state);
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} while (get64(&state->state_entry_time) != state_time);
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rmb(); /* Hypervisor might update data. */
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} while (get64(&state->state_entry_time) != state_time ||
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(state_time & XEN_RUNSTATE_UPDATE));
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}
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/*
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* Runstate accounting
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*/
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void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
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{
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xen_get_runstate_snapshot_cpu(res, smp_processor_id());
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}
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/* return true when a vcpu could run but has no real cpu to run on */
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@ -80,8 +84,7 @@ static u64 xen_steal_clock(int cpu)
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{
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struct vcpu_runstate_info state;
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BUG_ON(cpu != smp_processor_id());
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xen_get_runstate_snapshot(&state);
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xen_get_runstate_snapshot_cpu(&state, cpu);
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return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
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}
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@ -98,11 +101,14 @@ void xen_setup_runstate_info(int cpu)
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void __init xen_time_setup_guest(void)
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{
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bool xen_runstate_remote;
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xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
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VMASST_TYPE_runstate_update_flag);
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pv_time_ops.steal_clock = xen_steal_clock;
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static_key_slow_inc(¶virt_steal_enabled);
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/*
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* We can't set paravirt_steal_rq_enabled as this would require the
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* capability to read another cpu's runstate info.
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*/
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if (xen_runstate_remote)
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static_key_slow_inc(¶virt_steal_rq_enabled);
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}
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