KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put

When the VHE code was reworked, a lot of the vgic stuff was moved around,
but the GICv4 residency code did stay untouched, meaning that we come
in and out of residency on each flush/sync, which is obviously suboptimal.

To address this, let's move things around a bit:

- Residency entry (flush) moves to vcpu_load
- Residency exit (sync) moves to vcpu_put
- On blocking (entry to WFI), we "put"
- On unblocking (exit from WFI), we "load"

Because these can nest (load/block/put/load/unblock/put, for example),
we now have per-VPE tracking of the residency state.

Additionally, vgic_v4_put gains a "need doorbell" parameter, which only
gets set to true when blocking because of a WFI. This allows a finer
control of the doorbell, which now also gets disabled as soon as
it gets signaled.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191027144234.8395-2-maz@kernel.org

1 files changed, 26 insertions, 29 deletions

diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index 477af6aebb97..7e1f3202968a 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -85,6 +85,10 @@ static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
 {
 	struct kvm_vcpu *vcpu = info;
 
+	/* We got the message, no need to fire again */
+	if (!irqd_irq_disabled(&irq_to_desc(irq)->irq_data))
+		disable_irq_nosync(irq);
+
 	vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
 	kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
 	kvm_vcpu_kick(vcpu);
@@ -192,20 +196,30 @@ void vgic_v4_teardown(struct kvm *kvm)
 	its_vm->vpes = NULL;
 }
 
-int vgic_v4_sync_hwstate(struct kvm_vcpu *vcpu)
+int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db)
 {
-	if (!vgic_supports_direct_msis(vcpu->kvm))
+	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
+	struct irq_desc *desc = irq_to_desc(vpe->irq);
+
+	if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
 		return 0;
 
-	return its_schedule_vpe(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe, false);
+	/*
+	 * If blocking, a doorbell is required. Undo the nested
+	 * disable_irq() calls...
+	 */
+	while (need_db && irqd_irq_disabled(&desc->irq_data))
+		enable_irq(vpe->irq);
+
+	return its_schedule_vpe(vpe, false);
 }
 
-int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu)
+int vgic_v4_load(struct kvm_vcpu *vcpu)
 {
-	int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
+	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 	int err;
 
-	if (!vgic_supports_direct_msis(vcpu->kvm))
+	if (!vgic_supports_direct_msis(vcpu->kvm) || vpe->resident)
 		return 0;
 
 	/*
@@ -214,11 +228,14 @@ int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu)
 	 * doc in drivers/irqchip/irq-gic-v4.c to understand how this
 	 * turns into a VMOVP command at the ITS level.
 	 */
-	err = irq_set_affinity(irq, cpumask_of(smp_processor_id()));
+	err = irq_set_affinity(vpe->irq, cpumask_of(smp_processor_id()));
 	if (err)
 		return err;
 
-	err = its_schedule_vpe(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe, true);
+	/* Disabled the doorbell, as we're about to enter the guest */
+	disable_irq_nosync(vpe->irq);
+
+	err = its_schedule_vpe(vpe, true);
 	if (err)
 		return err;
 
@@ -226,9 +243,7 @@ int vgic_v4_flush_hwstate(struct kvm_vcpu *vcpu)
 	 * Now that the VPE is resident, let's get rid of a potential
 	 * doorbell interrupt that would still be pending.
 	 */
-	err = irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING, false);
-
-	return err;
+	return irq_set_irqchip_state(vpe->irq, IRQCHIP_STATE_PENDING, false);
 }
 
 static struct vgic_its *vgic_get_its(struct kvm *kvm,
@@ -335,21 +350,3 @@ out:
 	mutex_unlock(&its->its_lock);
 	return ret;
 }
-
-void kvm_vgic_v4_enable_doorbell(struct kvm_vcpu *vcpu)
-{
-	if (vgic_supports_direct_msis(vcpu->kvm)) {
-		int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
-		if (irq)
-			enable_irq(irq);
-	}
-}
-
-void kvm_vgic_v4_disable_doorbell(struct kvm_vcpu *vcpu)
-{
-	if (vgic_supports_direct_msis(vcpu->kvm)) {
-		int irq = vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq;
-		if (irq)
-			disable_irq(irq);
-	}
-}