[Xen-devel] [PATCH 11/12] Use xen_vcpuop_clockevent, xen_clocksource and xen wallclock.

[stefano.stabellini@xxxxxxxxxxxxx]

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

Use xen_vcpuop_clockevent instead of hpet and APIC timers as main
clockevent device on all vcpus, use the xen wallclock time as wallclock
instead of rtc and use xen_clocksource as clocksource.
The pv clock algorithm needs to work correctly for the xen_clocksource
and xen wallclock to be usable, only modern Xen versions offer a
reliable pv clock in HVM guests (XENFEAT_hvm_safe_pvclock).

Using the hpet as clocksource means a VMEXIT every time we read/write to
the hpet mmio addresses, pvclock give us a better rating without
VMEXITs. Same goes for the xen wallclock and xen_vcpuop_clockevent

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 arch/x86/xen/enlighten.c         |   31 +++++++++++++++++++++++++++++++
 arch/x86/xen/suspend.c           |    4 ++++
 include/xen/interface/features.h |    3 +++
 3 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c71b0fa..e90dfcd 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1307,6 +1307,36 @@ static struct notifier_block __cpuinitdata 
xen_hvm_cpu_notifier = {
        .notifier_call  = xen_hvm_cpu_notify,
 };
 
+static void xen_hvm_setup_cpu_clockevents(void)
+{
+       int cpu = smp_processor_id();
+       xen_setup_runstate_info(cpu);
+       xen_setup_timer(cpu);
+       xen_setup_cpu_clockevents();
+}
+
+static void init_hvm_time(void)
+{
+       /* vector callback is needed otherwise we cannot receive interrupts
+        * on cpu > 0 */
+       if (!xen_have_vector_callback && num_present_cpus() > 1)
+               return;
+       if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
+               printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
+                               "disable pv timer\n");
+               return;
+       }
+
+       pv_time_ops = xen_time_ops;
+       x86_init.timers.timer_init = xen_time_init;
+       x86_init.timers.setup_percpu_clockev = x86_init_noop;
+       x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
+
+       x86_platform.calibrate_tsc = xen_tsc_khz;
+       x86_platform.get_wallclock = xen_get_wallclock;
+       x86_platform.set_wallclock = xen_set_wallclock;
+}
+
 void __init xen_guest_init(void)
 {
        int r;
@@ -1326,4 +1356,5 @@ void __init xen_guest_init(void)
        register_cpu_notifier(&xen_hvm_cpu_notifier);
        have_vcpu_info_placement = 0;
        x86_init.irqs.intr_init = xen_init_IRQ;
+       init_hvm_time();
 }
diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
index 6ff9665..0774c67 100644
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -28,8 +28,12 @@ void xen_pre_suspend(void)
 
 void xen_hvm_post_suspend(int suspend_cancelled)
 {
+       int cpu;
        xen_hvm_init_shared_info();
        xen_callback_vector();
+       for_each_online_cpu(cpu) {
+               xen_setup_runstate_info(cpu);
+       }
 }
 
 void xen_post_suspend(int suspend_cancelled)
diff --git a/include/xen/interface/features.h b/include/xen/interface/features.h
index 8ab08b9..70d2563 100644
--- a/include/xen/interface/features.h
+++ b/include/xen/interface/features.h
@@ -44,6 +44,9 @@
 /* x86: Does this Xen host support the HVM callback vector type? */
 #define XENFEAT_hvm_callback_vector        8
 
+/* x86: pvclock algorithm is safe to use on HVM */
+#define XENFEAT_hvm_safe_pvclock           9
+
 #define XENFEAT_NR_SUBMAPS 1
 
 #endif /* __XEN_PUBLIC_FEATURES_H__ */
-- 
1.7.0.4


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