[Xen-devel] [PATCH 3/3] xen/arm: set the system time in Xen via the XENPF_settime hypercall

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

If Linux is running as dom0, call XENPF_settime to update the system
time in Xen on pvclock_gtod notifications.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 arch/arm/xen/enlighten.c |   52 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index b6aea9c..0176db0 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -28,6 +28,7 @@
 #include <linux/cpufreq.h>
 #include <linux/cpu.h>
 #include <linux/console.h>
+#include <linux/pvclock_gtod.h>
 #include <linux/timekeeping.h>
 #include <clocksource/arm_arch_timer.h>
 
@@ -123,6 +124,50 @@ static void xen_read_wallclock(struct timespec *ts)
        set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
 }
 
+static int xen_pvclock_gtod_notify(struct notifier_block *nb,
+                                  unsigned long was_set, void *priv)
+{
+       /* Protected by the calling core code serialization */
+       static struct timespec next_sync;
+
+       struct xen_platform_op op;
+       struct timespec now;
+
+       now = __current_kernel_time();
+
+       /*
+        * We only take the expensive HV call when the clock was set
+        * or when the 11 minutes RTC synchronization time elapsed.
+        */
+       if (!was_set && timespec_compare(&now, &next_sync) < 0)
+               return NOTIFY_OK;
+
+       op.interface_version = XENPF_INTERFACE_VERSION;
+       op.cmd = XENPF_settime;
+       op.u.settime.secs = now.tv_sec;
+       op.u.settime.nsecs = now.tv_nsec;
+       op.u.settime.system_time = arch_timer_read_counter();
+       printk("GTOD: Setting to %ld.%ld at %lld\n",
+              (long)op.u.settime.secs,
+              (long)op.u.settime.nsecs,
+              (long long)op.u.settime.system_time);
+       (void)HYPERVISOR_dom0_op(&op);
+
+       /*
+        * Move the next drift compensation time 11 minutes
+        * ahead. That's emulating the sync_cmos_clock() update for
+        * the hardware RTC.
+        */
+       next_sync = now;
+       next_sync.tv_sec += 11 * 60;
+
+       return NOTIFY_OK;
+}
+
+static struct notifier_block xen_pvclock_gtod_notifier = {
+       .notifier_call = xen_pvclock_gtod_notify,
+};
+
 static void xen_percpu_init(void)
 {
        struct vcpu_register_vcpu_info info;
@@ -321,7 +366,12 @@ static int __init xen_guest_init(void)
        pv_time_ops.steal_clock = xen_stolen_accounting;
        static_key_slow_inc(&paravirt_steal_enabled);
        xen_read_wallclock(&ts);
-       do_settimeofday(&ts);
+       if (xen_initial_domain())
+               pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
+       else {
+               xen_read_wallclock(&ts);
+               do_settimeofday(&ts);
+       }
 
        return 0;
 }
-- 
1.7.10.4


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