2 * Xen stolen ticks accounting.
4 #include <linux/kernel.h>
5 #include <linux/kernel_stat.h>
6 #include <linux/math64.h>
9 #include <asm/paravirt.h>
10 #include <asm/xen/hypervisor.h>
11 #include <asm/xen/hypercall.h>
13 #include <xen/events.h>
14 #include <xen/features.h>
15 #include <xen/interface/xen.h>
16 #include <xen/interface/vcpu.h>
17 #include <xen/xen-ops.h>
19 /* runstate info updated by Xen */
20 static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
22 /* return an consistent snapshot of 64-bit time/counter value */
23 static u64 get64(const u64 *p)
27 if (BITS_PER_LONG < 64) {
32 * Read high then low, and then make sure high is
33 * still the same; this will only loop if low wraps
34 * and carries into high.
35 * XXX some clean way to make this endian-proof?
38 h = READ_ONCE(p32[1]);
39 l = READ_ONCE(p32[0]);
40 h2 = READ_ONCE(p32[1]);
43 ret = (((u64)h) << 32) | l;
53 void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
56 struct vcpu_runstate_info *state;
58 BUG_ON(preemptible());
60 state = this_cpu_ptr(&xen_runstate);
63 * The runstate info is always updated by the hypervisor on
64 * the current CPU, so there's no need to use anything
65 * stronger than a compiler barrier when fetching it.
68 state_time = get64(&state->state_entry_time);
69 *res = READ_ONCE(*state);
70 } while (get64(&state->state_entry_time) != state_time);
73 /* return true when a vcpu could run but has no real cpu to run on */
74 bool xen_vcpu_stolen(int vcpu)
76 return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
79 static u64 xen_steal_clock(int cpu)
81 struct vcpu_runstate_info state;
83 BUG_ON(cpu != smp_processor_id());
84 xen_get_runstate_snapshot(&state);
85 return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
88 void xen_setup_runstate_info(int cpu)
90 struct vcpu_register_runstate_memory_area area;
92 area.addr.v = &per_cpu(xen_runstate, cpu);
94 if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
99 void __init xen_time_setup_guest(void)
101 pv_time_ops.steal_clock = xen_steal_clock;
103 static_key_slow_inc(¶virt_steal_enabled);
105 * We can't set paravirt_steal_rq_enabled as this would require the
106 * capability to read another cpu's runstate info.