On Mon, Dec 16, 2013 at 12:53:37PM +0000, Marc Zyngier wrote:
> On 12/12/13 19:55, Christoffer Dall wrote:
> > To properly access the VGIC state from user space it is very unpractical
> > to have to loop through all the LRs in all register access functions.
> > Instead, support moving all pending state from LRs to the distributor,
> > but leave active state LRs alone.
> >
> > Note that to accurately present the active and pending state to VCPUs
> > reading these distributor registers from a live VM, we would have to
> > stop all other VPUs than the calling VCPU and ask each CPU to unqueue
> > their LR state onto the distributor and add fields to track active state
> > on the distributor side as well. We don't have any users of such
> > functionality yet and there are other inaccuracies of the GIC emulation,
> > so don't provide accurate synchronized access to this state just yet.
> > However, when the time comes, having this function should help.
> >
> > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> > ---
> > Changelog[v4]:
> > - Reworked vgic_unqueue_irqs to explicitly check for the active bit and
> > to not use __test_and_clear_bit.
> >
> > Changelog[v3]:
> > - New patch in series
> >
> > virt/kvm/arm/vgic.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 81 insertions(+), 5 deletions(-)
> >
> > diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> > index 88599b5..8067e76 100644
> > --- a/virt/kvm/arm/vgic.c
> > +++ b/virt/kvm/arm/vgic.c
> > @@ -589,6 +589,78 @@ static bool handle_mmio_sgi_reg(struct kvm_vcpu *vcpu,
> > return false;
> > }
> >
> > +#define LR_CPUID(lr) \
> > + (((lr) & GICH_LR_PHYSID_CPUID) >> GICH_LR_PHYSID_CPUID_SHIFT)
> > +#define LR_IRQID(lr) \
> > + ((lr) & GICH_LR_VIRTUALID)
> > +
> > +static void vgic_retire_lr(int lr_nr, int irq, struct vgic_cpu *vgic_cpu)
> > +{
> > + clear_bit(lr_nr, vgic_cpu->lr_used);
> > + vgic_cpu->vgic_lr[lr_nr] &= ~GICH_LR_STATE;
> > + vgic_cpu->vgic_irq_lr_map[irq] = LR_EMPTY;
> > +}
> > +
> > +/**
> > + * vgic_unqueue_irqs - move pending IRQs from LRs to the distributor
> > + * @vgic_cpu: Pointer to the vgic_cpu struct holding the LRs
> > + *
> > + * Move any pending IRQs that have already been assigned to LRs back to the
> > + * emulated distributor state so that the complete emulated state can be read
> > + * from the main emulation structures without investigating the LRs.
> > + *
> > + * Note that IRQs in the active state in the LRs get their pending state moved
> > + * to the distributor but the active state stays in the LRs, because we don't
> > + * track the active state on the distributor side.
> > + */
> > +static void vgic_unqueue_irqs(struct kvm_vcpu *vcpu)
> > +{
> > + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> > + struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
> > + int vcpu_id = vcpu->vcpu_id;
> > + int i, irq, source_cpu;
> > + u32 *lr;
> > +
> > + for_each_set_bit(i, vgic_cpu->lr_used, vgic_cpu->nr_lr) {
> > + lr = &vgic_cpu->vgic_lr[i];
> > + irq = LR_IRQID(*lr);
> > + source_cpu = LR_CPUID(*lr);
> > +
> > + /*
> > + * There are three options for the state bits:
> > + *
> > + * 01: pending
> > + * 10: active
> > + * 11: pending and active
> > + *
> > + * If the LR holds only an active interrupt (not pending) then
> > + * just leave it alone.
> > + */
> > + if ((*lr & GICH_LR_STATE) == GICH_LR_ACTIVE_BIT)
> > + continue;
> > +
> > + /*
> > + * If the interrupt was only pending (not "active" or "pending
> > + * and active") then we the pending state will get moved to
> ^^ extra 'we'
> > + * the distributor and the LR does not hold any info and can
> > + * be marked as free for other use.
> > + */
> > + if ((*lr & GICH_LR_STATE) == GICH_LR_PENDING_BIT)
> > + vgic_retire_lr(i, irq, vgic_cpu);
>
> We should handle the ACTIVE+PENDING case, and I don't think we do.
> Should it be (*lr & GICH_LR_PENDING_BIT)? I think the previous version
> handled this case correctly.
>
nice catch! We just need to always clear the pending bit on the LR.
I'll fix that in a re-spin.
-Christoffer
> > + /*
> > + * Finally, reestablish the pending state on the distributor
> > + * and the CPU interface. It may have already been pending,
> > + * but that is fine, then we are only setting a few bits that
> > + * were already set.
> > + */
> > + vgic_dist_irq_set(vcpu, irq);
> > + if (irq < VGIC_NR_SGIS)
> > + dist->irq_sgi_sources[vcpu_id][irq] |= 1 << source_cpu;
> > + vgic_update_state(vcpu->kvm);
> > + }
> > +}
> > +
> > static bool handle_mmio_sgi_clear(struct kvm_vcpu *vcpu,
> > struct kvm_exit_mmio *mmio,
> > phys_addr_t offset)
> > @@ -848,8 +920,6 @@ static void vgic_update_state(struct kvm *kvm)
> > }
> > }
> >
> > -#define LR_CPUID(lr) \
> > - (((lr) & GICH_LR_PHYSID_CPUID) >> GICH_LR_PHYSID_CPUID_SHIFT)
> > #define MK_LR_PEND(src, irq) \
> > (GICH_LR_PENDING_BIT | ((src) << GICH_LR_PHYSID_CPUID_SHIFT) | (irq))
> >
> > @@ -871,9 +941,7 @@ static void vgic_retire_disabled_irqs(struct kvm_vcpu *vcpu)
> > int irq = vgic_cpu->vgic_lr[lr] & GICH_LR_VIRTUALID;
> >
> > if (!vgic_irq_is_enabled(vcpu, irq)) {
> > - vgic_cpu->vgic_irq_lr_map[irq] = LR_EMPTY;
> > - clear_bit(lr, vgic_cpu->lr_used);
> > - vgic_cpu->vgic_lr[lr] &= ~GICH_LR_STATE;
> > + vgic_retire_lr(lr, irq, vgic_cpu);
> > if (vgic_irq_is_active(vcpu, irq))
> > vgic_irq_clear_active(vcpu, irq);
> > }
> > @@ -1675,6 +1743,14 @@ static int vgic_attr_regs_access(struct kvm_device *dev,
> > }
> > }
> >
> > + /*
> > + * Move all pending IRQs from the LRs on all VCPUs so the pending
> > + * state can be properly represented in the register state accessible
> > + * through this API.
> > + */
> > + kvm_for_each_vcpu(c, tmp_vcpu, dev->kvm)
> > + vgic_unqueue_irqs(tmp_vcpu);
> > +
> > offset -= r->base;
> > r->handle_mmio(vcpu, &mmio, offset);
> >
> >
>
>
> --
> Jazz is not dead. It just smells funny...
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--
Christoffer
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