| Message ID | 1368027714-14506-4-git-send-email-stefano.stabellini@eu.citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Stefano, On 08/05/13 16:41, Stefano Stabellini wrote: > Register the runstate_memory_area with the hypervisor. > Use pv_time_ops.steal_clock to account for stolen ticks. > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > > Changes in v3: > - use BUG_ON and smp_processor_id. > --- > arch/arm/xen/enlighten.c | 22 ++++++++++++++++++++++ > 1 files changed, 22 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c > index 13609e0..dfa7738 100644 > --- a/arch/arm/xen/enlighten.c > +++ b/arch/arm/xen/enlighten.c > @@ -14,7 +14,10 @@ > #include <xen/xen-ops.h> > #include <asm/xen/hypervisor.h> > #include <asm/xen/hypercall.h> > +#include <asm/arch_timer.h> > #include <asm/system_misc.h> > +#include <asm/paravirt.h> > +#include <linux/jump_label.h> > #include <linux/interrupt.h> > #include <linux/irqreturn.h> > #include <linux/module.h> > @@ -152,6 +155,19 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma, > } > EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range); > > +unsigned long long xen_stolen_accounting(int cpu) > +{ > + struct vcpu_runstate_info state; > + > + BUG_ON(cpu != smp_processor_id()); > + > + xen_get_runstate_snapshot(&state); > + > + WARN_ON(state.state != RUNSTATE_running); > + > + return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline]; > +} > + > static void __init xen_percpu_init(void *unused) > { > struct vcpu_register_vcpu_info info; > @@ -169,6 +185,8 @@ static void __init xen_percpu_init(void *unused) > BUG_ON(err); > per_cpu(xen_vcpu, cpu) = vcpup; > > + xen_setup_runstate_info(cpu); > + > enable_percpu_irq(xen_events_irq, 0); > } > > @@ -300,6 +318,10 @@ static int __init xen_init_events(void) > > on_each_cpu(xen_percpu_init, NULL, 0); > > + pv_time_ops.steal_clock = xen_stolen_accounting; What guarantee do we have that this is done before the rest of the kernel calls paravirt_steal_clock()? What if we have Xen support enabled but don't run as a Xen guest? > + static_key_slow_inc(¶virt_steal_enabled); > + static_key_slow_inc(¶virt_steal_rq_enabled); > + > return 0; > } > postcore_initcall(xen_init_events); > Thanks, M.
On Wed, 8 May 2013, Marc Zyngier wrote: > Hi Stefano, > > On 08/05/13 16:41, Stefano Stabellini wrote: > > Register the runstate_memory_area with the hypervisor. > > Use pv_time_ops.steal_clock to account for stolen ticks. > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > > > > Changes in v3: > > - use BUG_ON and smp_processor_id. > > --- > > arch/arm/xen/enlighten.c | 22 ++++++++++++++++++++++ > > 1 files changed, 22 insertions(+), 0 deletions(-) > > > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c > > index 13609e0..dfa7738 100644 > > --- a/arch/arm/xen/enlighten.c > > +++ b/arch/arm/xen/enlighten.c > > @@ -14,7 +14,10 @@ > > #include <xen/xen-ops.h> > > #include <asm/xen/hypervisor.h> > > #include <asm/xen/hypercall.h> > > +#include <asm/arch_timer.h> > > #include <asm/system_misc.h> > > +#include <asm/paravirt.h> > > +#include <linux/jump_label.h> > > #include <linux/interrupt.h> > > #include <linux/irqreturn.h> > > #include <linux/module.h> > > @@ -152,6 +155,19 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma, > > } > > EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range); > > > > +unsigned long long xen_stolen_accounting(int cpu) > > +{ > > + struct vcpu_runstate_info state; > > + > > + BUG_ON(cpu != smp_processor_id()); > > + > > + xen_get_runstate_snapshot(&state); > > + > > + WARN_ON(state.state != RUNSTATE_running); > > + > > + return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline]; > > +} > > + > > static void __init xen_percpu_init(void *unused) > > { > > struct vcpu_register_vcpu_info info; > > @@ -169,6 +185,8 @@ static void __init xen_percpu_init(void *unused) > > BUG_ON(err); > > per_cpu(xen_vcpu, cpu) = vcpup; > > > > + xen_setup_runstate_info(cpu); > > + > > enable_percpu_irq(xen_events_irq, 0); > > } > > > > @@ -300,6 +318,10 @@ static int __init xen_init_events(void) > > > > on_each_cpu(xen_percpu_init, NULL, 0); > > > > + pv_time_ops.steal_clock = xen_stolen_accounting; > > What guarantee do we have that this is done before the rest of the > kernel calls paravirt_steal_clock()? That's not a problem: paravirt_steal_clock is not called unless paravirt_steal_enabled or paravirt_steal_rq_enabled are set. Also steal_clock is always increasing so loosing the first few updates is not an issue. > What if we have Xen support enabled but don't run as a Xen guest? That's fine as long as the Xen runstate_memory_area interface is available. Usually I am a great fun of feature flags, so that every feature can be dynamically enabled or disabled and an hypervisor interface can be only partially implemented. However the runstate_memory_area is very old and I would consider it one of the core interfaces that need to be available in order to claim "Xen compatibility". > > + static_key_slow_inc(¶virt_steal_enabled); > > + static_key_slow_inc(¶virt_steal_rq_enabled); > > + > > return 0; > > } > > postcore_initcall(xen_init_events); > >
On Wed, 2013-05-08 at 18:03 +0100, Stefano Stabellini wrote: > > What if we have Xen support enabled but don't run as a Xen guest? > > That's fine as long as the Xen runstate_memory_area interface is > available. > Usually I am a great fun of feature flags, so that every feature can be > dynamically enabled or disabled and an hypervisor interface can be only > partially implemented. > > However the runstate_memory_area is very old and I would consider it > one of the core interfaces that need to be available in order to claim > "Xen compatibility". I think Marc meant "what if CONFIG_XEN=y but we are running on KVM?". In that case we wont have set either of the paravirt_steal*_enabled static keys and so the hook won't be called. > > > + static_key_slow_inc(¶virt_steal_enabled); > > > + static_key_slow_inc(¶virt_steal_rq_enabled); > > > + Ian.
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c index 13609e0..dfa7738 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -14,7 +14,10 @@ #include <xen/xen-ops.h> #include <asm/xen/hypervisor.h> #include <asm/xen/hypercall.h> +#include <asm/arch_timer.h> #include <asm/system_misc.h> +#include <asm/paravirt.h> +#include <linux/jump_label.h> #include <linux/interrupt.h> #include <linux/irqreturn.h> #include <linux/module.h> @@ -152,6 +155,19 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma, } EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range); +unsigned long long xen_stolen_accounting(int cpu) +{ + struct vcpu_runstate_info state; + + BUG_ON(cpu != smp_processor_id()); + + xen_get_runstate_snapshot(&state); + + WARN_ON(state.state != RUNSTATE_running); + + return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline]; +} + static void __init xen_percpu_init(void *unused) { struct vcpu_register_vcpu_info info; @@ -169,6 +185,8 @@ static void __init xen_percpu_init(void *unused) BUG_ON(err); per_cpu(xen_vcpu, cpu) = vcpup; + xen_setup_runstate_info(cpu); + enable_percpu_irq(xen_events_irq, 0); } @@ -300,6 +318,10 @@ static int __init xen_init_events(void) on_each_cpu(xen_percpu_init, NULL, 0); + pv_time_ops.steal_clock = xen_stolen_accounting; + static_key_slow_inc(¶virt_steal_enabled); + static_key_slow_inc(¶virt_steal_rq_enabled); + return 0; } postcore_initcall(xen_init_events);
Register the runstate_memory_area with the hypervisor. Use pv_time_ops.steal_clock to account for stolen ticks. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Changes in v3: - use BUG_ON and smp_processor_id. --- arch/arm/xen/enlighten.c | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-)