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Diffstat (limited to 'arch/x86/xen/time.c')
-rw-r--r--arch/x86/xen/time.c99
1 files changed, 98 insertions, 1 deletions
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 80c2a4bdf230..29163c43ebbd 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -75,7 +75,7 @@ static void xen_get_wallclock(struct timespec *now)
static int xen_set_wallclock(const struct timespec *now)
{
- return -1;
+ return -ENODEV;
}
static int xen_pvclock_gtod_notify(struct notifier_block *nb,
@@ -371,8 +371,95 @@ static const struct pv_time_ops xen_time_ops __initconst = {
.steal_clock = xen_steal_clock,
};
+static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
+
+void xen_save_time_memory_area(void)
+{
+ struct vcpu_register_time_memory_area t;
+ int ret;
+
+ if (!xen_clock)
+ return;
+
+ t.addr.v = NULL;
+
+ ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
+ if (ret != 0)
+ pr_notice("Cannot save secondary vcpu_time_info (err %d)",
+ ret);
+ else
+ clear_page(xen_clock);
+}
+
+void xen_restore_time_memory_area(void)
+{
+ struct vcpu_register_time_memory_area t;
+ int ret;
+
+ if (!xen_clock)
+ return;
+
+ t.addr.v = &xen_clock->pvti;
+
+ ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
+
+ /*
+ * We don't disable VCLOCK_PVCLOCK entirely if it fails to register the
+ * secondary time info with Xen or if we migrated to a host without the
+ * necessary flags. On both of these cases what happens is either
+ * process seeing a zeroed out pvti or seeing no PVCLOCK_TSC_STABLE_BIT
+ * bit set. Userspace checks the latter and if 0, it discards the data
+ * in pvti and fallbacks to a system call for a reliable timestamp.
+ */
+ if (ret != 0)
+ pr_notice("Cannot restore secondary vcpu_time_info (err %d)",
+ ret);
+}
+
+static void xen_setup_vsyscall_time_info(void)
+{
+ struct vcpu_register_time_memory_area t;
+ struct pvclock_vsyscall_time_info *ti;
+ int ret;
+
+ ti = (struct pvclock_vsyscall_time_info *)get_zeroed_page(GFP_KERNEL);
+ if (!ti)
+ return;
+
+ t.addr.v = &ti->pvti;
+
+ ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
+ if (ret) {
+ pr_notice("xen: VCLOCK_PVCLOCK not supported (err %d)\n", ret);
+ free_page((unsigned long)ti);
+ return;
+ }
+
+ /*
+ * If primary time info had this bit set, secondary should too since
+ * it's the same data on both just different memory regions. But we
+ * still check it in case hypervisor is buggy.
+ */
+ if (!(ti->pvti.flags & PVCLOCK_TSC_STABLE_BIT)) {
+ t.addr.v = NULL;
+ ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area,
+ 0, &t);
+ if (!ret)
+ free_page((unsigned long)ti);
+
+ pr_notice("xen: VCLOCK_PVCLOCK not supported (tsc unstable)\n");
+ return;
+ }
+
+ xen_clock = ti;
+ pvclock_set_pvti_cpu0_va(xen_clock);
+
+ xen_clocksource.archdata.vclock_mode = VCLOCK_PVCLOCK;
+}
+
static void __init xen_time_init(void)
{
+ struct pvclock_vcpu_time_info *pvti;
int cpu = smp_processor_id();
struct timespec tp;
@@ -396,6 +483,16 @@ static void __init xen_time_init(void)
setup_force_cpu_cap(X86_FEATURE_TSC);
+ /*
+ * We check ahead on the primary time info if this
+ * bit is supported hence speeding up Xen clocksource.
+ */
+ pvti = &__this_cpu_read(xen_vcpu)->time;
+ if (pvti->flags & PVCLOCK_TSC_STABLE_BIT) {
+ pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+ xen_setup_vsyscall_time_info();
+ }
+
xen_setup_runstate_info(cpu);
xen_setup_timer(cpu);
xen_setup_cpu_clockevents();