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Date: Thu, 01 Jul 2010 15:41:17 -0400
From: Don Dutile <ddutile@...hat.com>
To: stefano@...bellini.net
CC: linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
Stefano.Stabellini@...citrix.com, sheng@...ux.intel.com,
jeremy@...p.org
Subject: Re: [PATCH 11/13] Use xen_vcpuop_clockevent, xen_clocksource and
xen wallclock.
stefano@...bellini.net wrote:
> From: Stefano Stabellini <stefano.stabellini@...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@...citrix.com>
> ---
> arch/x86/xen/enlighten.c | 14 +--------
> arch/x86/xen/suspend.c | 4 ++
> arch/x86/xen/time.c | 59 ++++++++++++++++++++++++++++++++++---
> arch/x86/xen/xen-ops.h | 7 +---
> include/xen/interface/features.h | 3 ++
> 5 files changed, 65 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 90bac21..bcd98a9 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -933,10 +933,6 @@ static const struct pv_init_ops xen_init_ops __initdata = {
> .patch = xen_patch,
> };
>
> -static const struct pv_time_ops xen_time_ops __initdata = {
> - .sched_clock = xen_sched_clock,
> -};
> -
> static const struct pv_cpu_ops xen_cpu_ops __initdata = {
> .cpuid = xen_cpuid,
>
> @@ -1074,7 +1070,6 @@ asmlinkage void __init xen_start_kernel(void)
> /* Install Xen paravirt ops */
> pv_info = xen_info;
> pv_init_ops = xen_init_ops;
> - pv_time_ops = xen_time_ops;
> pv_cpu_ops = xen_cpu_ops;
> pv_apic_ops = xen_apic_ops;
>
> @@ -1082,13 +1077,7 @@ asmlinkage void __init xen_start_kernel(void)
> x86_init.oem.arch_setup = xen_arch_setup;
> x86_init.oem.banner = xen_banner;
>
> - 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;
> + xen_init_time_ops();
>
> /*
> * Set up some pagetable state before starting to set any ptes.
> @@ -1330,4 +1319,5 @@ void __init xen_hvm_guest_init(void)
> register_cpu_notifier(&xen_hvm_cpu_notifier);
> have_vcpu_info_placement = 0;
> x86_init.irqs.intr_init = xen_init_IRQ;
> + xen_hvm_init_time_ops();
> }
> 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);
> + }
> }
>
As I found out on older xen (non 'modern Xen version' ;-) )
w/o XENFEAT_hvm_safe_pvclock, the above patch should look like:
if (xen_feature(XENFEAT_hvm_safe_pvclock)) {
int cpu;
for_each_online_cpu(cpu) {
xen_setup_runstate_info(cpu);
}
}
- Don
> void xen_post_suspend(int suspend_cancelled)
> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
> index 32764b8..2d76c28 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();
>
> @@ -497,3 +502,47 @@ __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.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;
> +}
> +
> diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
> index 01c9dd3..089d189 100644
> --- a/arch/x86/xen/xen-ops.h
> +++ b/arch/x86/xen/xen-ops.h
> @@ -49,11 +49,8 @@ void xen_setup_runstate_info(int cpu);
> void xen_teardown_timer(int cpu);
> cycle_t xen_clocksource_read(void);
> void xen_setup_cpu_clockevents(void);
> -unsigned long xen_tsc_khz(void);
> -void __init xen_time_init(void);
> -unsigned long xen_get_wallclock(void);
> -int xen_set_wallclock(unsigned long time);
> -unsigned long long xen_sched_clock(void);
> +void __init xen_init_time_ops(void);
> +void __init xen_hvm_init_time_ops(void);
>
> irqreturn_t xen_debug_interrupt(int irq, void *dev_id);
>
> 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__ */
--
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