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    Subject[PATCH][v8 6/7] xen: Enable PV clocksource for HVM
    Date
    PV clocksource can provide a reliable clocksource for HVM running on Xen.

    To enable it, put following line to the HVM configure file:

    cpuid = [ '0x40000002:edx=0x3' ]

    It would set bit 0 and bit 1 in 0x40000002:edx, which enable PV extension
    framework and PV clocksource.

    Signed-off-by: Sheng Yang <sheng@linux.intel.com>
    ---
    arch/x86/xen/hvmpv.c | 24 ++++++++++++++++++++++++
    arch/x86/xen/time.c | 12 +++++++++++-
    arch/x86/xen/xen-ops.h | 1 +
    3 files changed, 36 insertions(+), 1 deletions(-)

    diff --git a/arch/x86/xen/hvmpv.c b/arch/x86/xen/hvmpv.c
    index 0b200b7..792d740 100644
    --- a/arch/x86/xen/hvmpv.c
    +++ b/arch/x86/xen/hvmpv.c
    @@ -43,6 +43,8 @@ static void __init xen_hvm_pv_banner(void)
    pv_info.name);
    printk(KERN_INFO "Xen version: %d.%d%s\n",
    version >> 16, version & 0xffff, extra.extraversion);
    + if (xen_hvm_pv_clock_enabled())
    + printk(KERN_INFO "PV feature: PV clocksource enabled\n");
    }

    static int __init xen_para_available(void)
    @@ -81,6 +83,9 @@ static int __init init_hvm_pv_info(void)
    if (!(edx & XEN_CPUID_FEAT2_HVM_PV))
    return -ENODEV;

    + if (edx & XEN_CPUID_FEAT2_HVM_PV_CLOCK)
    + xen_hvm_pv_features |= XEN_HVM_PV_CLOCK_ENABLED;
    +
    if (pages < 1)
    return -ENODEV;

    @@ -111,6 +116,23 @@ static int __init init_shared_info(void)
    return 0;
    }

    +static void __init init_pv_clocksource(void)
    +{
    + if (!xen_hvm_pv_clock_enabled())
    + return;
    +
    + if (enable_hvm_pv(HVM_PV_CLOCK))
    + BUG();
    +
    + pv_time_ops.sched_clock = xen_sched_clock;
    +
    + x86_platform.calibrate_tsc = xen_tsc_khz;
    + x86_platform.get_wallclock = xen_get_wallclock;
    + x86_platform.set_wallclock = xen_set_wallclock;
    +
    + xen_register_clocksource();
    +}
    +
    void __init xen_guest_init(void)
    {
    int r;
    @@ -133,4 +155,6 @@ void __init xen_guest_init(void)
    pv_info = xen_hvm_pv_info;

    xen_domain_type = XEN_HVM_DOMAIN;
    +
    + init_pv_clocksource();
    }
    diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
    index 0d3f07c..06b3e72 100644
    --- a/arch/x86/xen/time.c
    +++ b/arch/x86/xen/time.c
    @@ -472,11 +472,21 @@ void xen_timer_resume(void)
    }
    }

    +static bool xen_clocksource_enabled;
    +
    +void xen_register_clocksource(void)
    +{
    + if (!xen_clocksource_enabled) {
    + clocksource_register(&xen_clocksource);
    + xen_clocksource_enabled = 1;
    + }
    +}
    +
    __init void xen_time_init(void)
    {
    int cpu = smp_processor_id();

    - clocksource_register(&xen_clocksource);
    + xen_register_clocksource();

    if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
    /* Successfully turned off 100Hz tick, so we have the
    diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
    index f9153a3..d56b660 100644
    --- a/arch/x86/xen/xen-ops.h
    +++ b/arch/x86/xen/xen-ops.h
    @@ -48,6 +48,7 @@ cycle_t xen_clocksource_read(void);
    void xen_setup_cpu_clockevents(void);
    unsigned long xen_tsc_khz(void);
    void __init xen_time_init(void);
    +void xen_register_clocksource(void);
    unsigned long xen_get_wallclock(void);
    int xen_set_wallclock(unsigned long time);
    unsigned long long xen_sched_clock(void);
    --
    1.7.0.1


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