On Thu, 24 Jan 2019 13:59:38 +0100 Michael Mueller <[email protected]> wrote:
> The patch implements a handler for GIB alert interruptions > on the host. Its task is to alert guests that interrupts are > pending for them. > > A GIB alert interrupt statistic counter is added as well: > > $ cat /proc/interrupts > CPU0 CPU1 > ... > GAL: 23 37 [I/O] GIB Alert > ... > > Signed-off-by: Michael Mueller <[email protected]> [..] > +/** > + * gisa_get_ipm_or_restore_iam - return IPM or restore GISA IAM > + * > + * @gi: gisa interrupt struct to work on > + * > + * Atomically restores the interruption alert mask if none of the > + * relevant ISCs are pending and return the IPM. The word 'relevant' probably reflects some previous state. It does not bother me too much. [..] > > +static void __airqs_kick_single_vcpu(struct kvm *kvm, u8 deliverable_mask) > +{ > + int vcpu_id, online_vcpus = atomic_read(&kvm->online_vcpus); > + struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int; > + struct kvm_vcpu *vcpu; > + > + for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) { > + vcpu = kvm_get_vcpu(kvm, vcpu_id); > + if (psw_ioint_disabled(vcpu)) > + continue; > + deliverable_mask &= (u8)(vcpu->arch.sie_block->gcr[6] >> 24); > + if (deliverable_mask) { > + /* lately kicked but not yet running */ How about /* was kicked but didn't run yet */? > + if (test_and_set_bit(vcpu_id, gi->kicked_mask)) > + return; > + kvm_s390_vcpu_wakeup(vcpu); > + return; > + } > + } > +} > + [..] > +static void process_gib_alert_list(void) > +{ > + struct kvm_s390_gisa_interrupt *gi; > + struct kvm_s390_gisa *gisa; > + struct kvm *kvm; > + u32 final, origin = 0UL; > + > + do { > + /* > + * If the NONE_GISA_ADDR is still stored in the alert list > + * origin, we will leave the outer loop. No further GISA has > + * been added to the alert list by millicode while processing > + * the current alert list. > + */ > + final = (origin & NONE_GISA_ADDR); > + /* > + * Cut off the alert list and store the NONE_GISA_ADDR in the > + * alert list origin to avoid further GAL interruptions. > + * A new alert list can be build up by millicode in parallel > + * for guests not in the yet cut-off alert list. When in the > + * final loop, store the NULL_GISA_ADDR instead. This will re- > + * enable GAL interruptions on the host again. > + */ > + origin = xchg(&gib->alert_list_origin, > + (!final) ? NONE_GISA_ADDR : NULL_GISA_ADDR); > + /* > + * Loop through the just cut-off alert list and start the > + * gisa timers to kick idle vcpus to consume the pending > + * interruptions asap. > + */ > + while (origin & GISA_ADDR_MASK) { > + gisa = (struct kvm_s390_gisa *)(u64)origin; > + origin = gisa->next_alert; > + gisa->next_alert = (u32)(u64)gisa; > + kvm = container_of(gisa, struct sie_page2, gisa)->kvm; > + gi = &kvm->arch.gisa_int; > + if (hrtimer_active(&gi->timer)) > + hrtimer_cancel(&gi->timer); > + hrtimer_start(&gi->timer, 0, HRTIMER_MODE_REL); > + } > + } while (!final); > + > +} > + > void kvm_s390_gisa_clear(struct kvm *kvm) > { > struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int; > > if (!gi->origin) > return; > - memset(gi->origin, 0, sizeof(struct kvm_s390_gisa)); > - gi->origin->next_alert = (u32)(u64)gi->origin; > + gisa_clear_ipm(gi->origin); This could be a separate patch. I would like little more explanation to this. > VM_EVENT(kvm, 3, "gisa 0x%pK cleared", gi->origin); > } > > @@ -2940,13 +3078,25 @@ void kvm_s390_gisa_init(struct kvm *kvm) > gi->origin = &kvm->arch.sie_page2->gisa; > gi->alert.mask = 0; > spin_lock_init(&gi->alert.ref_lock); > - kvm_s390_gisa_clear(kvm); > + gi->expires = 50 * 1000; /* 50 usec */ I blindly trust your choice here ;) > + hrtimer_init(&gi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > + gi->timer.function = gisa_vcpu_kicker; > + memset(gi->origin, 0, sizeof(struct kvm_s390_gisa)); > + gi->origin->next_alert = (u32)(u64)gi->origin; > VM_EVENT(kvm, 3, "gisa 0x%pK initialized", gi->origin); > } > > void kvm_s390_gisa_destroy(struct kvm *kvm) > { > - kvm->arch.gisa_int.origin = NULL; > + struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int; > + > + if (!gi->origin) > + return; > + hrtimer_cancel(&gi->timer); I'm not sure this cancel here is sufficient. > + WRITE_ONCE(gi->alert.mask, 0); > + while (gisa_in_alert_list(gi->origin)) > + cpu_relax(); If you end up waiting here, I guess, it's likely that a new timer is going to get set up right after we do gisa->next_alert = (u32)(u64)gisa; in process_gib_alert_list(). > + gi->origin = NULL; > } > > /** > @@ -3037,11 +3187,23 @@ int kvm_s390_gisc_unregister(struct kvm *kvm, u32 > gisc) > } > EXPORT_SYMBOL_GPL(kvm_s390_gisc_unregister); > Overall, there are couple of things I would prefer done differently, but better something working today that something prefect in 6 months. In that sense, provided my comment regarding destroy is addressed: Acked-by: Halil Pasic <[email protected]>
