KVM: arm64: vgic-v4: Restore pending state on host userspace write

When the VMM writes to ISPENDR0 to set the state pending state of
an SGI, we fail to convey this to the HW if this SGI is already
backed by a GICv4.1 vSGI.

This is a bit of a corner case, as this would only occur if the
vgic state is changed on an already running VM, but this can
apparently happen across a guest reset driven by the VMM.

Fix this by always writing out the pending_latch value to the
HW, and reseting it to false.

Reported-by: Kunkun Jiang <jiangkunkun@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Cc: stable@vger.kernel.org # 5.10+
Link: https://lore.kernel.org/r/7e7f2c0c-448b-10a9-8929-4b8f4f6e2a32@huawei.com

Author: Marc Zyngier

arch/arm64/kvm/vgic/vgic-mmio-v3.c

@@ -365,19 +365,26 @@ static int vgic_v3_uaccess_write_pending(struct kvm_vcpu *vcpu,
 		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
 
 		raw_spin_lock_irqsave(&irq->irq_lock, flags);
-		if (test_bit(i, &val)) {
-			/*
-			 * pending_latch is set irrespective of irq type
-			 * (level or edge) to avoid dependency that VM should
-			 * restore irq config before pending info.
-			 */
-			irq->pending_latch = true;
-			vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
-		} else {
+
+		/*
+		 * pending_latch is set irrespective of irq type
+		 * (level or edge) to avoid dependency that VM should
+		 * restore irq config before pending info.
+		 */
+		irq->pending_latch = test_bit(i, &val);
+
+		if (irq->hw && vgic_irq_is_sgi(irq->intid)) {
+			irq_set_irqchip_state(irq->host_irq,
+					      IRQCHIP_STATE_PENDING,
+					      irq->pending_latch);
 			irq->pending_latch = false;
-			raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
 		}
 
+		if (irq->pending_latch)
+			vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
+		else
+			raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
+
 		vgic_put_irq(vcpu->kvm, irq);
 	}