[v4,6/7] xen/arm: set the system time in Xen via the XENPF_settime64 hypercall

Commit Message

Stefano Stabellini Nov. 12, 2015, 5:30 p.m. UTC

If Linux is running as dom0, call XENPF_settime64 to update the system
time in Xen on pvclock_gtod notifications.

Signed-off-by: Stefano Stabellini <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>

---

Changes in v3:
- s/%llu.%0u/%llu.%09u
- in xen_pvclock_gtod_notify use the passed struct timekeeper pointer
  rather than calling __current_kernel_time64
- use the passed struct timekeeper pointer to get the system time too

Changes in v2:
- properly convert arch_timer ticker to nsec
- rename dom0_op to platform_op
- use timespec64 interfaces
- use XENPF_settime64
---
 arch/arm/xen/enlighten.c |   55 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

Comments

Julien Grall Nov. 13, 2015, 1:56 p.m. UTC | #1

On 12/11/15 17:30, Stefano Stabellini wrote:
> +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 timespec64 next_sync;
> +
> +	struct xen_platform_op op;
> +	struct timespec64 now, system_time;
> +	struct timekeeper *tk = priv;
> +
> +	now.tv_sec = tk->xtime_sec;
> +	now.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
> +	system_time = timespec64_add(now, tk->wall_to_monotonic);
> +
> +	/*
> +	 * We only take the expensive HV call when the clock was set
> +	 * or when the 11 minutes RTC synchronization time elapsed.
> +	 */
> +	if (!was_set && timespec64_compare(&now, &next_sync) < 0)
> +		return NOTIFY_OK;
> +
> +	op.interface_version = XENPF_INTERFACE_VERSION;
> +	op.cmd = XENPF_settime64;
> +	op.u.settime64.mbz = 0;
> +	op.u.settime64.secs = now.tv_sec;
> +	op.u.settime64.nsecs = now.tv_nsec;
> +	op.u.settime64.system_time = timespec64_to_ns(&system_time);
> +	printk("GTOD: Setting to %llu.%09u at %llu\n",
> +	       op.u.settime64.secs,
> +	       op.u.settime64.nsecs,
> +	       op.u.settime64.system_time);

Is this printk really useful?

> +	(void)HYPERVISOR_platform_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;
> @@ -313,7 +364,9 @@ static int __init xen_guest_init(void)
>  
>  	pv_time_ops.steal_clock = xen_stolen_accounting;
>  	static_key_slow_inc(&paravirt_steal_enabled);
> -
> +	if (xen_initial_domain())
> +		pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
> + 

I think, you've introduced a trailing whitespace.

>  	return 0;
>  }
>  early_initcall(xen_guest_init);
> 

Regards,

Patch

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 6ae4ef5..613f7e0 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -28,7 +28,10 @@ 
 #include <linux/cpufreq.h>
 #include <linux/cpu.h>
 #include <linux/console.h>
+#include <linux/pvclock_gtod.h>
+#include <linux/time64.h>
 #include <linux/timekeeping.h>
+#include <linux/timekeeper_internal.h>
 
 #include <linux/mm.h>
 
@@ -117,6 +120,54 @@  static void xen_read_wallclock(struct timespec64 *ts)
 	*ts = timespec64_add(now, ts_monotonic);
 }
 
+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 timespec64 next_sync;
+
+	struct xen_platform_op op;
+	struct timespec64 now, system_time;
+	struct timekeeper *tk = priv;
+
+	now.tv_sec = tk->xtime_sec;
+	now.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
+	system_time = timespec64_add(now, tk->wall_to_monotonic);
+
+	/*
+	 * We only take the expensive HV call when the clock was set
+	 * or when the 11 minutes RTC synchronization time elapsed.
+	 */
+	if (!was_set && timespec64_compare(&now, &next_sync) < 0)
+		return NOTIFY_OK;
+
+	op.interface_version = XENPF_INTERFACE_VERSION;
+	op.cmd = XENPF_settime64;
+	op.u.settime64.mbz = 0;
+	op.u.settime64.secs = now.tv_sec;
+	op.u.settime64.nsecs = now.tv_nsec;
+	op.u.settime64.system_time = timespec64_to_ns(&system_time);
+	printk("GTOD: Setting to %llu.%09u at %llu\n",
+	       op.u.settime64.secs,
+	       op.u.settime64.nsecs,
+	       op.u.settime64.system_time);
+	(void)HYPERVISOR_platform_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;
@@ -313,7 +364,9 @@  static int __init xen_guest_init(void)
 
 	pv_time_ops.steal_clock = xen_stolen_accounting;
 	static_key_slow_inc(&paravirt_steal_enabled);
-
+	if (xen_initial_domain())
+		pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
+ 
 	return 0;
 }
 early_initcall(xen_guest_init);