[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] xen: merge temporary vcpu pinning scenarios
On 23/07/2019 10:20, Juergen Gross wrote: > Today there are three scenarios which are pinning vcpus temporarily to > a single physical cpu: > > - NMI/MCE injection into PV domains > - wait_event() handling > - vcpu_pin_override() handling > > Each of those cases are handled independently today using their own > temporary cpumask to save the old affinity settings. > > The three cases can be combined as the two latter cases will only pin > a vcpu to the physical cpu it is already running on, while > vcpu_pin_override() is allowed to fail. > > So merge the three temporary pinning scenarios by only using one > cpumask and a per-vcpu bitmask for specifying which of the three > scenarios is currently active (they are allowed to nest). > > Note that we don't need to call domain_update_node_affinity() as we > are only pinning for a brief period of time. > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx> > --- > xen/arch/x86/pv/traps.c | 20 +------------------- > xen/arch/x86/traps.c | 8 ++------ > xen/common/domain.c | 4 +--- > xen/common/schedule.c | 35 +++++++++++++++++++++++------------ > xen/common/wait.c | 26 ++++++++------------------ > xen/include/xen/sched.h | 8 +++++--- > 6 files changed, 40 insertions(+), 61 deletions(-) > > diff --git a/xen/arch/x86/pv/traps.c b/xen/arch/x86/pv/traps.c > index 1740784ff2..37dac300ba 100644 > --- a/xen/arch/x86/pv/traps.c > +++ b/xen/arch/x86/pv/traps.c > @@ -151,25 +151,7 @@ static void nmi_mce_softirq(void) > > BUG_ON(st->vcpu == NULL); > > - /* > - * Set the tmp value unconditionally, so that the check in the iret > - * hypercall works. > - */ > - cpumask_copy(st->vcpu->cpu_hard_affinity_tmp, > - st->vcpu->cpu_hard_affinity); > - > - if ( (cpu != st->processor) || > - (st->processor != st->vcpu->processor) ) > - { > - > - /* > - * We are on a different physical cpu. Make sure to wakeup the vcpu > on > - * the specified processor. > - */ > - vcpu_set_hard_affinity(st->vcpu, cpumask_of(st->processor)); > - > - /* Affinity is restored in the iret hypercall. */ > - } > + vcpu_set_tmp_affinity(st->vcpu, st->processor, VCPU_AFFINITY_NMI); Please can we keep the comment explaining where the affinity is restored, which is a disguised explanation of why it is PV-only. > diff --git a/xen/common/schedule.c b/xen/common/schedule.c > index 89bc259ae4..d4de74f9c8 100644 > --- a/xen/common/schedule.c > +++ b/xen/common/schedule.c > @@ -1106,47 +1106,58 @@ void watchdog_domain_destroy(struct domain *d) > kill_timer(&d->watchdog_timer[i]); > } > > -int vcpu_pin_override(struct vcpu *v, int cpu) > +int vcpu_set_tmp_affinity(struct vcpu *v, int cpu, uint8_t reason) > { > spinlock_t *lock; > int ret = -EINVAL; > + bool migrate; > > lock = vcpu_schedule_lock_irq(v); > > if ( cpu < 0 ) > { > - if ( v->affinity_broken ) > + if ( v->affinity_broken & reason ) > { > - sched_set_affinity(v, v->cpu_hard_affinity_saved, NULL); > - v->affinity_broken = 0; > ret = 0; > + v->affinity_broken &= ~reason; > } > + if ( !ret && !v->affinity_broken ) > + sched_set_affinity(v, v->cpu_hard_affinity_saved, NULL); > } > else if ( cpu < nr_cpu_ids ) > { > - if ( v->affinity_broken ) > + if ( (v->affinity_broken & reason) || > + (v->affinity_broken && v->processor != cpu) ) > ret = -EBUSY; > else if ( cpumask_test_cpu(cpu, VCPU2ONLINE(v)) ) > { > - cpumask_copy(v->cpu_hard_affinity_saved, v->cpu_hard_affinity); > - v->affinity_broken = 1; > - sched_set_affinity(v, cpumask_of(cpu), NULL); > + if ( !v->affinity_broken ) > + { > + cpumask_copy(v->cpu_hard_affinity_saved, > v->cpu_hard_affinity); > + sched_set_affinity(v, cpumask_of(cpu), NULL); > + } > + v->affinity_broken |= reason; > ret = 0; > } > } > > - if ( ret == 0 ) > + migrate = !ret && !cpumask_test_cpu(v->processor, v->cpu_hard_affinity); > + if ( migrate ) > vcpu_migrate_start(v); > > vcpu_schedule_unlock_irq(lock, v); > > - domain_update_node_affinity(v->domain); > - > - vcpu_migrate_finish(v); > + if ( migrate ) > + vcpu_migrate_finish(v); > > return ret; > } > > +int vcpu_pin_override(struct vcpu *v, int cpu) There are exactly two callers of vcpu_pin_override(). I'd take the opportunity to make vcpu_set_tmp_affinity() the single API call for adjusting affinity. > +{ > + return vcpu_set_tmp_affinity(v, cpu, VCPU_AFFINITY_OVERRIDE); > +} > + > typedef long ret_t; > > #endif /* !COMPAT */ > diff --git a/xen/common/wait.c b/xen/common/wait.c > index 4f830a14e8..9f9ad033b3 100644 > --- a/xen/common/wait.c > +++ b/xen/common/wait.c > @@ -182,30 +178,24 @@ static void __prepare_to_wait(struct waitqueue_vcpu > *wqv) > static void __finish_wait(struct waitqueue_vcpu *wqv) > { > wqv->esp = NULL; > - (void)vcpu_set_hard_affinity(current, &wqv->saved_affinity); > + vcpu_set_tmp_affinity(current, -1, VCPU_AFFINITY_WAIT); > } > > void check_wakeup_from_wait(void) > { > - struct waitqueue_vcpu *wqv = current->waitqueue_vcpu; > + struct vcpu *curr = current; > + struct waitqueue_vcpu *wqv = curr->waitqueue_vcpu; > > ASSERT(list_empty(&wqv->list)); > > if ( likely(wqv->esp == NULL) ) > return; > > - /* Check if we woke up on the wrong CPU. */ > - if ( unlikely(smp_processor_id() != wqv->wakeup_cpu) ) > + /* Check if we are still pinned. */ > + if ( unlikely(!(curr->affinity_broken & VCPU_AFFINITY_WAIT)) ) > { > - /* Re-set VCPU affinity and re-enter the scheduler. */ > - struct vcpu *curr = current; > - cpumask_copy(&wqv->saved_affinity, curr->cpu_hard_affinity); > - if ( vcpu_set_hard_affinity(curr, cpumask_of(wqv->wakeup_cpu)) ) > - { > - gdprintk(XENLOG_ERR, "Unable to set vcpu affinity\n"); > - domain_crash(current->domain); > - } > - wait(); /* takes us back into the scheduler */ > + gdprintk(XENLOG_ERR, "vcpu affinity lost\n"); > + domain_crash(current->domain); curr > } > > /* > diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h > index b40c8fd138..721c429454 100644 > --- a/xen/include/xen/sched.h > +++ b/xen/include/xen/sched.h > @@ -200,7 +200,10 @@ struct vcpu > /* VCPU is paused following shutdown request (d->is_shutting_down)? */ > bool paused_for_shutdown; > /* VCPU need affinity restored */ > - bool affinity_broken; > + uint8_t affinity_broken; > +#define VCPU_AFFINITY_OVERRIDE 0x01 > +#define VCPU_AFFINITY_NMI 0x02 VCPU_AFFINITY_NMI_MCE ? It is used for more than just NMIs. ~Andrew > +#define VCPU_AFFINITY_WAIT 0x04 > > /* A hypercall has been preempted. */ > bool hcall_preempted; > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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