vfio: Fix PCI INTx disable consistency

The virq_disabled flag tracks the userspace view of INTx masking
across interrupt mode changes, but we're not consistently applying
this to the interrupt and masking handler notion of the device.
Currently if the user sets DisINTx while in MSI or MSIX mode, then
returns to INTx mode (ex. rebooting a qemu guest), the hardware has
DisINTx+, but the management of INTx thinks it's enabled, making it
impossible to actually clear DisINTx.  Fix this by updating the
handler state when INTx is re-enabled.

Cc: stable@vger.kernel.org
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/vfio_pci_intrs.c

@@ -366,6 +366,17 @@ static int vfio_intx_enable(struct vfio_pci_device *vdev)
 		return -ENOMEM;
 
 	vdev->num_ctx = 1;
+
+	/*
+	 * If the virtual interrupt is masked, restore it.  Devices
+	 * supporting DisINTx can be masked at the hardware level
+	 * here, non-PCI-2.3 devices will have to wait until the
+	 * interrupt is enabled.
+	 */
+	vdev->ctx[0].masked = vdev->virq_disabled;
+	if (vdev->pci_2_3)
+		pci_intx(vdev->pdev, !vdev->ctx[0].masked);
+
 	vdev->irq_type = VFIO_PCI_INTX_IRQ_INDEX;
 
 	return 0;
@@ -419,7 +430,7 @@ static int vfio_intx_set_signal(struct vfio_pci_device *vdev, int fd)
 	 * disable_irq won't.
 	 */
 	spin_lock_irqsave(&vdev->irqlock, flags);
-	if (!vdev->pci_2_3 && (vdev->ctx[0].masked || vdev->virq_disabled))
+	if (!vdev->pci_2_3 && vdev->ctx[0].masked)
 		disable_irq_nosync(pdev->irq);
 	spin_unlock_irqrestore(&vdev->irqlock, flags);