[PATCH v3 26/55] KVM: arm/arm64: vgic-new: Add ACTIVE registers handlers

[Andre Przywara <andre.przywara@arm.com>]

The active register handlers are shared between the v2 and v3
emulation, so their implementation goes into vgic-mmio.c, to be
easily referenced from the v3 emulation as well later.
Since activation/deactivation of an interrupt may happen entirely
in the guest without it ever exiting, we need some extra logic to
properly track the active state.
Putting it on an ap_list on activation is similar to the normal case
handled by vgic_queue_irq_unlock(), but differs in some details that
make a separate implementation worthwhile.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
Changelog RFC..v1:
- handling queueing in write handler
- remove IRQ lock from read handler

Changelog v1 .. v2:
- adapt to new MMIO framework

 virt/kvm/arm/vgic/vgic-mmio-v2.c |   4 +-
 virt/kvm/arm/vgic/vgic-mmio.c    | 120 +++++++++++++++++++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic-mmio.h    |  10 ++++
 3 files changed, 132 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c
index 4b87e0a..054b52d 100644
--- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
+++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
@@ -80,9 +80,9 @@ static const struct vgic_register_region vgic_v2_dist_registers[] = {
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_PENDING_CLEAR,
 		vgic_mmio_read_pending, vgic_mmio_write_cpending, 1),
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_ACTIVE_SET,
-		vgic_mmio_read_raz, vgic_mmio_write_wi, 1),
+		vgic_mmio_read_active, vgic_mmio_write_sactive, 1),
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_ACTIVE_CLEAR,
-		vgic_mmio_read_raz, vgic_mmio_write_wi, 1),
+		vgic_mmio_read_active, vgic_mmio_write_cactive, 1),
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_PRI,
 		vgic_mmio_read_raz, vgic_mmio_write_wi, 8),
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_TARGET,
diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 4df1af7..dbf683e 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -162,6 +162,126 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 	}
 }
 
+unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
+				    gpa_t addr, unsigned int len)
+{
+	u32 intid = (addr & 0x7f) * 8;
+	u32 value = 0;
+	int i;
+
+	/* Loop over all IRQs affected by this read */
+	for (i = 0; i < len * 8; i++) {
+		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
+
+		if (irq->active)
+			value |= (1U << i);
+	}
+
+	return extract_bytes(value, addr & 3, len);
+}
+
+void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
+			     gpa_t addr, unsigned int len,
+			     unsigned long val)
+{
+	u32 intid = (addr & 0x7f) * 8;
+	int i;
+
+	for_each_set_bit(i, &val, len * 8) {
+		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
+
+		spin_lock(&irq->irq_lock);
+
+		irq->active = false;
+
+		/*
+		 * Christoffer wrote:
+		 * The question is what to do if the vcpu for this irq is
+		 * running and the LR there has the active bit set, then we'll
+		 * overwrite this change when we fold the LR state back into
+		 * the vgic_irq struct.
+		 *
+		 * Since I expect this to be extremely rare, one option is to
+		 * force irq->vcpu to exit (if non-null) and then do you
+		 * thing here after you've confirm it has exited while holding
+		 * some lock preventing it from re-entering again.
+		 * Slightly crazy.
+		 *
+		 * The alternative is to put a big fat comment nothing that
+		 * this is non-supported bad race, and wait until someone
+		 * submits a bug report relating to this...
+		 */
+
+		spin_unlock(&irq->irq_lock);
+	}
+}
+
+void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
+			     gpa_t addr, unsigned int len,
+			     unsigned long val)
+{
+	u32 intid = (addr & 0x7f) * 8;
+	int i;
+
+	for_each_set_bit(i, &val, len * 8) {
+		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
+
+		spin_lock(&irq->irq_lock);
+
+		/* As this is a special case, we can't use the
+		 * vgic_queue_irq_unlock() function to put this on a VCPU.
+		 * So deal with this here explicitly unless the IRQs was
+		 * already active, it was on a VCPU before or there is no
+		 * target VCPU assigned at the moment.
+		 */
+		if (irq->active || irq->vcpu || !irq->target_vcpu) {
+			irq->active = true;
+
+			spin_unlock(&irq->irq_lock);
+			continue;
+		}
+
+		spin_unlock(&irq->irq_lock);
+retry:
+		vcpu = irq->target_vcpu;
+
+		spin_lock(&vcpu->arch.vgic_cpu.ap_list_lock);
+		spin_lock(&irq->irq_lock);
+
+		/*
+		 * Recheck after dropping the IRQ lock to see if we should
+		 * still care about queueing it.
+		 */
+		if (irq->active || irq->vcpu) {
+			irq->active = true;
+
+			spin_unlock(&irq->irq_lock);
+			spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
+
+			continue;
+		}
+
+		/* Did the target VCPU change while we had the lock dropped? */
+		if (vcpu != irq->target_vcpu) {
+			spin_unlock(&irq->irq_lock);
+			spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
+
+			goto retry;
+		}
+
+		/* Now queue the IRQ to the VCPU's ap_list. */
+		list_add_tail(&irq->ap_list, &vcpu->arch.vgic_cpu.ap_list_head);
+		irq->vcpu = vcpu;
+
+		irq->active = true;
+
+		spin_unlock(&irq->irq_lock);
+		spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
+
+		kvm_vcpu_kick(vcpu);
+	}
+}
+
 static int match_region(const void *key, const void *elt)
 {
 	const unsigned int offset = (unsigned long)key;
diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
index d4fc029..fa875dc 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.h
+++ b/virt/kvm/arm/vgic/vgic-mmio.h
@@ -96,6 +96,16 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val);
 
+unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
+				    gpa_t addr, unsigned int len);
+
+void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
+			     gpa_t addr, unsigned int len,
+			     unsigned long val);
+
+void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
+			     gpa_t addr, unsigned int len,
+			     unsigned long val);
 
 unsigned int vgic_v2_init_dist_iodev(struct vgic_io_device *dev);
 
-- 
2.7.3