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 <jgr...@suse.com>
> ---
> 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;
>
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