[PATCH v2 6/7] xen/arm: introduce xen_read_wallclock

Stefano Stabellini
2015-11-10T11:57:54Z

Read the wallclock from the shared info page at boot time.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---

Changes in v2:
- properly convert arch_timer ticker to nsec
- use timespec64 interfaces
- use sec_hi to get a 64-bit seconds value
---
arch/arm/Kconfig | 1 +
arch/arm/xen/enlighten.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 60be104..a9de420 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1852,6 +1852,7 @@ config XEN
depends on CPU_V7 && !CPU_V6
depends on !GENERIC_ATOMIC64
depends on MMU
+ depends on HAVE_ARM_ARCH_TIMER
select ARCH_DMA_ADDR_T_64BIT
select ARM_PSCI
select SWIOTLB_XEN
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 2f57ba3..32675b5 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -28,6 +28,8 @@
#include <linux/cpufreq.h>
#include <linux/cpu.h>
#include <linux/console.h>
+#include <linux/timekeeping.h>
+#include <clocksource/arm_arch_timer.h>

#include <linux/mm.h>

@@ -95,6 +97,34 @@ static unsigned long long xen_stolen_accounting(int cpu)
return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
}

+static void xen_read_wallclock(struct timespec64 *ts)
+{
+ u32 version;
+ u64 delta;
+ struct timespec64 now;
+ struct shared_info *s = HYPERVISOR_shared_info;
+ struct pvclock_wall_clock *wall_clock = &(s->wc);
+
+ /* get wallclock at system boot */
+ do {
+ version = wall_clock->version;
+ rmb(); /* fetch version before time */
+ now.tv_sec = ((uint64_t)wall_clock->sec_hi << 32) | wall_clock->sec;
+ now.tv_nsec = wall_clock->nsec;
+ rmb(); /* fetch time before checking version */
+ } while ((wall_clock->version & 1) || (version != wall_clock->version));
+
+ delta = arch_timer_read_counter() * (u64)NSEC_PER_SEC;
+ do_div(delta, arch_timer_get_rate()); /* time since system boot */
+ delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
+
+ now.tv_nsec = do_div(delta, NSEC_PER_SEC);
+ now.tv_sec = delta;
+
+ set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec);
+
+}
+
static void xen_percpu_init(void)
{
struct vcpu_register_vcpu_info info;
@@ -218,6 +248,7 @@ static int __init xen_guest_init(void)
struct shared_info *shared_info_page = NULL;
struct resource res;
phys_addr_t grant_frames;
+ struct timespec64 ts;

if (!xen_domain())
return 0;
@@ -291,6 +322,8 @@ 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_settimeofday64(&ts);

return 0;
}
--
1.7.10.4