[PATCH v3 11/11] KVM: arm/arm64: vgic: Allow HW interrupts for non-shared devices
Christoffer Dall
christoffer.dall at linaro.org
Tue Aug 4 11:07:49 PDT 2015
On Tue, Aug 04, 2015 at 06:08:53PM +0100, Marc Zyngier wrote:
> On 04/08/15 15:32, Christoffer Dall wrote:
> > On Fri, Jul 24, 2015 at 04:55:09PM +0100, Marc Zyngier wrote:
> >> So far, the only use of the HW interrupt facility is the timer,
> >> implying that the active state is context-switched for each vcpu,
> >> as the device is is shared across all vcpus.
> >>
> >> This does not work for a device that has been assigned to a VM,
> >> as the guest is entierely in control of that device (the HW is
> >> not shared). In that case, it makes sense to bypass the whole
> >> active state switching, and only track the deactivation of the
> >> interrupt.
> >>
> >> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> >> ---
> >> include/kvm/arm_vgic.h | 6 ++--
> >> virt/kvm/arm/arch_timer.c | 3 +-
> >> virt/kvm/arm/vgic.c | 73 +++++++++++++++++++++++++++++++++++++----------
> >> 3 files changed, 64 insertions(+), 18 deletions(-)
> >>
> >> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> >> index f6bfd79..6f0a4e1 100644
> >> --- a/include/kvm/arm_vgic.h
> >> +++ b/include/kvm/arm_vgic.h
> >> @@ -164,7 +164,8 @@ struct irq_phys_map {
> >> u32 phys_irq;
> >> u32 irq;
> >> bool deleted;
> >> - bool active;
> >> + bool shared;
> >> + bool active; /* Only valid if shared */
> >> };
> >>
> >> struct irq_phys_map_entry {
> >> @@ -357,7 +358,8 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg);
> >> int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu);
> >> int kvm_vgic_vcpu_active_irq(struct kvm_vcpu *vcpu);
> >> struct irq_phys_map *kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu,
> >> - int virt_irq, int irq);
> >> + int virt_irq, int irq,
> >> + bool shared);
> >> int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, struct irq_phys_map *map);
> >> bool kvm_vgic_get_phys_irq_active(struct irq_phys_map *map);
> >> void kvm_vgic_set_phys_irq_active(struct irq_phys_map *map, bool active);
> >> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> >> index 76e38d2..db21d8f 100644
> >> --- a/virt/kvm/arm/arch_timer.c
> >> +++ b/virt/kvm/arm/arch_timer.c
> >> @@ -203,7 +203,8 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
> >> * Tell the VGIC that the virtual interrupt is tied to a
> >> * physical interrupt. We do that once per VCPU.
> >> */
> >> - map = kvm_vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq);
> >> + map = kvm_vgic_map_phys_irq(vcpu, irq->irq,
> >> + host_vtimer_irq, true);
> >> if (WARN_ON(IS_ERR(map)))
> >> return PTR_ERR(map);
> >>
> >> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> >> index e40ef70..5e6b816 100644
> >> --- a/virt/kvm/arm/vgic.c
> >> +++ b/virt/kvm/arm/vgic.c
> >> @@ -1128,19 +1128,25 @@ static void vgic_queue_irq_to_lr(struct kvm_vcpu *vcpu, int irq,
> >> * active in the physical world. Otherwise the
> >> * physical interrupt will fire and the guest will
> >> * exit before processing the virtual interrupt.
> >> + *
> >> + * This is of course only valid for a shared
> >> + * interrupt. A non shared interrupt should already be
> >> + * active.
> >> */
> >> if (map) {
> >> - int ret;
> >> -
> >> - BUG_ON(!map->active);
> >> vlr.hwirq = map->phys_irq;
> >> vlr.state |= LR_HW;
> >> vlr.state &= ~LR_EOI_INT;
> >>
> >> - ret = irq_set_irqchip_state(map->irq,
> >> - IRQCHIP_STATE_ACTIVE,
> >> - true);
> >> - WARN_ON(ret);
> >> + if (map->shared) {
> >> + int ret;
> >> +
> >> + BUG_ON(!map->active);
> >> + ret = irq_set_irqchip_state(map->irq,
> >> + IRQCHIP_STATE_ACTIVE,
> >> + true);
> >> + WARN_ON(ret);
> >> + }
> >>
> >> /*
> >> * Make sure we're not going to sample this
> >> @@ -1383,21 +1389,41 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
> >> static int vgic_sync_hwirq(struct kvm_vcpu *vcpu, struct vgic_lr vlr)
> >> {
> >> struct irq_phys_map *map;
> >> + bool active;
> >> int ret;
> >>
> >> if (!(vlr.state & LR_HW))
> >> return 0;
> >>
> >> map = vgic_irq_map_search(vcpu, vlr.irq);
> >> - BUG_ON(!map || !map->active);
> >> + BUG_ON(!map);
> >> + BUG_ON(map->shared && !map->active);
> >>
> >> ret = irq_get_irqchip_state(map->irq,
> >> IRQCHIP_STATE_ACTIVE,
> >> - &map->active);
> >> + &active);
> >>
> >> WARN_ON(ret);
> >>
> >> - if (map->active) {
> >> + /*
> >> + * For a non-shared interrupt, we have to cater for two
> >> + * possible deactivation conditions:
> >> + *
> >> + * - the physical interrupt is now inactive (EOIed from the
> >> + * guest)
> >
> > nit: whitespace funkyness
> >
> >> + * - the physical interrupt is still active, but its virtual
> >> + * counterpart is flagged as "not queued", indicating another
> >> + * interrupt has fired between the EOI and the guest exit.
> >> + *
> >> + * Also, we are not reactivating a non-shared interrupt
> >
> > what does reactivating mean? did you mean deactivate?
>
> Deactivate indeed.
>
> >> + * ourselves. This is always left to the guest.
> >
> > In which case, add ", because the device is solely owned by the guest."
>
> Sure.
>
> >> + */
> >> + if (!map->shared)
> >> + return !active || !vgic_irq_is_queued(vcpu, vlr.irq);
> >
> > do you really need the second part of the disjunction?
> >
> > The effect seems to be that we clear the queued flag once again, and
> > clear the LR. If we don't do this, won't we simply pick up the pending
> > flag next time we're about to run this VCPU and piggy-back on the
> > existing LR. Perhaps this is a weird flow though?
>
> Crucially, we free the LR in this case (the set_bit on elrsr_ptr). If we
> don't do this, we're indeed going to schedule the vcpu (it has something
> to process), but we never allow piggy-backing on level interrupts. We'd
> need some special hack to handle this.
>
> I definitely feel more comfortable reporting that the interrupt has been
> deactivated (which is the case), and let the normal flow pick up the
> next injected interrupt.
>
Yes, you're right, it's much better this way.
I assume you'll still wait with this stuff until the priority drop / EOI
stuff is in, so I'll do a formal review again once all the dependencies
are there.
But this looks good to me.
-Christoffer
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