On 09/04/2015 09:40 PM, Christoffer Dall wrote: > Currently vgic_process_maintenance() processes dealing with a completed > level-triggered interrupt directly, but we are soon going to reuse this > logic for level-triggered mapped interrupts with the HW bit set, so > move this logic into a separate static function. > > Probably the most scary part of this commit is convincing yourself that > the current flow is safe compared to the old one. In the following I > try to list the changes and why they are harmless: > > Move vgic_irq_clear_queued after kvm_notify_acked_irq: > Harmless because the effect of clearing the queued flag wrt. > kvm_set_irq is only that vgic_update_irq_pending does not set the > pending bit on the emulated CPU interface or in the pending_on_cpu > bitmask, well actually the notifier calls vgic_update_irq_pending with level ==0 so it does not reach the can_sample. but we set this in __kvm_vgic_sync_hwstate later on if the > level is stil high. still
Reviewed-by: Eric Auger <[email protected]> Eric > > Move vgic_set_lr before kvm_notify_acked_irq: > Also, harmless because the LR are cpu-local operations and > kvm_notify_acked only affects the dist > > Move vgic_dist_irq_clear_soft_pend after kvm_notify_acked_irq: > Also harmless because it's just a bit which is cleared and altering > the line state does not affect this bit. > > Reviewed-by: Marc Zyngier <[email protected]> > Signed-off-by: Christoffer Dall <[email protected]> > --- > virt/kvm/arm/vgic.c | 88 > ++++++++++++++++++++++++++++++----------------------- > 1 file changed, 50 insertions(+), 38 deletions(-) > > diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c > index 6bd1c9b..fe0e5db 100644 > --- a/virt/kvm/arm/vgic.c > +++ b/virt/kvm/arm/vgic.c > @@ -1322,12 +1322,56 @@ epilog: > } > } > > +static int process_level_irq(struct kvm_vcpu *vcpu, int lr, struct vgic_lr > vlr) > +{ > + int level_pending = 0; > + > + vlr.state = 0; > + vlr.hwirq = 0; > + vgic_set_lr(vcpu, lr, vlr); > + > + /* > + * If the IRQ was EOIed (called from vgic_process_maintenance) or it > + * went from active to non-active (called from vgic_sync_hwirq) it was > + * also ACKed and we we therefore assume we can clear the soft pending > + * state (should it had been set) for this interrupt. > + * > + * Note: if the IRQ soft pending state was set after the IRQ was > + * acked, it actually shouldn't be cleared, but we have no way of > + * knowing that unless we start trapping ACKs when the soft-pending > + * state is set. > + */ > + vgic_dist_irq_clear_soft_pend(vcpu, vlr.irq); > + > + /* > + * Tell the gic to start sampling the line of this interrupt again. > + */ > + vgic_irq_clear_queued(vcpu, vlr.irq); > + > + /* Any additional pending interrupt? */ > + if (vgic_dist_irq_get_level(vcpu, vlr.irq)) { > + vgic_cpu_irq_set(vcpu, vlr.irq); > + level_pending = 1; > + } else { > + vgic_dist_irq_clear_pending(vcpu, vlr.irq); > + vgic_cpu_irq_clear(vcpu, vlr.irq); > + } > + > + /* > + * Despite being EOIed, the LR may not have > + * been marked as empty. > + */ > + vgic_sync_lr_elrsr(vcpu, lr, vlr); > + > + return level_pending; > +} > + > static bool vgic_process_maintenance(struct kvm_vcpu *vcpu) > { > u32 status = vgic_get_interrupt_status(vcpu); > struct vgic_dist *dist = &vcpu->kvm->arch.vgic; > - bool level_pending = false; > struct kvm *kvm = vcpu->kvm; > + int level_pending = 0; > > kvm_debug("STATUS = %08x\n", status); > > @@ -1342,54 +1386,22 @@ static bool vgic_process_maintenance(struct kvm_vcpu > *vcpu) > > for_each_set_bit(lr, eisr_ptr, vgic->nr_lr) { > struct vgic_lr vlr = vgic_get_lr(vcpu, lr); > - WARN_ON(vgic_irq_is_edge(vcpu, vlr.irq)); > > - spin_lock(&dist->lock); > - vgic_irq_clear_queued(vcpu, vlr.irq); > + WARN_ON(vgic_irq_is_edge(vcpu, vlr.irq)); > WARN_ON(vlr.state & LR_STATE_MASK); > - vlr.state = 0; > - vgic_set_lr(vcpu, lr, vlr); > > - /* > - * If the IRQ was EOIed it was also ACKed and we we > - * therefore assume we can clear the soft pending > - * state (should it had been set) for this interrupt. > - * > - * Note: if the IRQ soft pending state was set after > - * the IRQ was acked, it actually shouldn't be > - * cleared, but we have no way of knowing that unless > - * we start trapping ACKs when the soft-pending state > - * is set. > - */ > - vgic_dist_irq_clear_soft_pend(vcpu, vlr.irq); > > /* > * kvm_notify_acked_irq calls kvm_set_irq() > - * to reset the IRQ level. Need to release the > - * lock for kvm_set_irq to grab it. > + * to reset the IRQ level, which grabs the dist->lock > + * so we call this before taking the dist->lock. > */ > - spin_unlock(&dist->lock); > - > kvm_notify_acked_irq(kvm, 0, > vlr.irq - VGIC_NR_PRIVATE_IRQS); > - spin_lock(&dist->lock); > - > - /* Any additional pending interrupt? */ > - if (vgic_dist_irq_get_level(vcpu, vlr.irq)) { > - vgic_cpu_irq_set(vcpu, vlr.irq); > - level_pending = true; > - } else { > - vgic_dist_irq_clear_pending(vcpu, vlr.irq); > - vgic_cpu_irq_clear(vcpu, vlr.irq); > - } > > + spin_lock(&dist->lock); > + level_pending |= process_level_irq(vcpu, lr, vlr); > spin_unlock(&dist->lock); > - > - /* > - * Despite being EOIed, the LR may not have > - * been marked as empty. > - */ > - vgic_sync_lr_elrsr(vcpu, lr, vlr); > } > } > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
