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    Subject[PATCH 11/12] Use xen_vcpuop_clockevent, xen_clocksource and xen wallclock.
    Date
    From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

    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>
    ---
    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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