[Xen-devel] [PATCH 3 of 5] pv clocksource

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Hi all,
this adds a PV clocksource that can provide a reliable clocksource for
Linux running as an HVM guest on Xen.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Signed-off-by: Sheng Yang <sheng@xxxxxxxxxxxxxxx>

---

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 42135e8..6292cc6 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1253,6 +1253,20 @@ static void __init init_shared_info(void)
        per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
 }
 
+static void __init init_pv_clocksource(void)
+{
+       if (!xen_hvm_domain())
+               return;
+
+       pv_time_ops.sched_clock = xen_sched_clock;
+
+       x86_platform.calibrate_tsc = xen_tsc_khz;
+       x86_platform.get_wallclock = xen_get_wallclock;
+       x86_platform.set_wallclock = xen_set_wallclock;
+
+       xen_register_clocksource();
+}
+
 void __init xen_guest_init(void)
 {
        int r;
@@ -1262,5 +1276,6 @@ void __init xen_guest_init(void)
                return;
 
        init_shared_info();
+       init_pv_clocksource();
 }
 
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 0a5aa44..d1c1c50 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -474,11 +474,21 @@ void xen_timer_resume(void)
        }
 }
 
+static bool xen_clocksource_enabled;
+
+void xen_register_clocksource(void)
+{
+       if (!xen_clocksource_enabled) {
+               clocksource_register(&xen_clocksource);
+               xen_clocksource_enabled = 1;
+       }
+}
+
 __init void xen_time_init(void)
 {
        int cpu = smp_processor_id();
 
-       clocksource_register(&xen_clocksource);
+       xen_register_clocksource();
 
        if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
                /* Successfully turned off 100Hz tick, so we have the
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 355fa6b..2aeaf51 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -46,6 +46,7 @@ cycle_t xen_clocksource_read(void);
 void xen_setup_cpu_clockevents(void);
 unsigned long xen_tsc_khz(void);
 void __init xen_time_init(void);
+void xen_register_clocksource(void);
 unsigned long xen_get_wallclock(void);
 int xen_set_wallclock(unsigned long time);
 unsigned long long xen_sched_clock(void);

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