x86: Use xen_vcpuop_clockevent, xen_clocksource and xen wallclock.

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@eu.citrix.com>
Signed-off-by: Don Dutile <ddutile@redhat.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 53 insertions, 5 deletions

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index b3c6c59ed30..4780e55886a 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -20,6 +20,7 @@
 #include <asm/xen/hypercall.h>
 
 #include <xen/events.h>
+#include <xen/features.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/vcpu.h>
 
@@ -160,7 +161,7 @@ static void do_stolen_accounting(void)
  * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED
  * states.
  */
-unsigned long long xen_sched_clock(void)
+static unsigned long long xen_sched_clock(void)
 {
         struct vcpu_runstate_info state;
         cycle_t now;
@@ -195,7 +196,7 @@ unsigned long long xen_sched_clock(void)
 
 
 /* Get the TSC speed from Xen */
-unsigned long xen_tsc_khz(void)
+static unsigned long xen_tsc_khz(void)
 {
         struct pvclock_vcpu_time_info *info =
                 &HYPERVISOR_shared_info->vcpu_info[0].time;
@@ -230,7 +231,7 @@ static void xen_read_wallclock(struct timespec *ts)
         put_cpu_var(xen_vcpu);
 }
 
-unsigned long xen_get_wallclock(void)
+static unsigned long xen_get_wallclock(void)
 {
         struct timespec ts;
 
@@ -238,7 +239,7 @@ unsigned long xen_get_wallclock(void)
         return ts.tv_sec;
 }
 
-int xen_set_wallclock(unsigned long now)
+static int xen_set_wallclock(unsigned long now)
 {
         /* do nothing for domU */
         return -1;
@@ -473,7 +474,11 @@ void xen_timer_resume(void)
         }
 }
 
-__init void xen_time_init(void)
+static const struct pv_time_ops xen_time_ops __initdata = {
+        .sched_clock = xen_sched_clock,
+};
+
+static __init void xen_time_init(void)
 {
         int cpu = smp_processor_id();
         struct timespec tp;
@@ -497,3 +502,46 @@ __init void xen_time_init(void)
         xen_setup_timer(cpu);
         xen_setup_cpu_clockevents();
 }
+
+__init void xen_init_time_ops(void)
+{
+        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 = x86_init_noop;
+
+        x86_platform.calibrate_tsc = xen_tsc_khz;
+        x86_platform.get_wallclock = xen_get_wallclock;
+        x86_platform.set_wallclock = xen_set_wallclock;
+}
+
+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();
+}
+
+__init void xen_hvm_init_time_ops(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.setup_percpu_clockev = xen_time_init;
+        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;
+}
+