virtio_pci: do not wait forvever at a reset

We all know how it's possible for a guest VM to access various host functions by accessing a PCI device, right? When KVM traps an access to this fake PCI, QEMU emulates the device, which allows packets sent, console updated, or whatever. This is called "virtio".

NVIDIA took it a step further: they have a real PCI device that emuilates QEMU. No joke. And, they have a firmware bug! The following patch works around it:

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 9193c30d640a..6bbb34f9b088 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -438,6 +438,7 @@ static void vp_reset(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
+	int i;
 
 	/* 0 status means a reset. */
 	vp_modern_set_status(mdev, 0);
@@ -446,8 +447,16 @@ static void vp_reset(struct virtio_device *vdev)
 	 * This will flush out the status write, and flush in device writes,
 	 * including MSI-X interrupts, if any.
 	 */
-	while (vp_modern_get_status(mdev))
+	i = 0;
+	while (vp_modern_get_status(mdev)) {
+		if (++i >= 10000) {
+			printk(KERN_INFO
+			       "virtio reset ignoring status 0x%02x\n",
+			       vp_modern_get_status(mdev));
+			break;
+		}
 		msleep(1);
+	}
 
 	vp_modern_avq_cleanup(vdev);
 

I'm not dumping on NVIDIA here at all, I think it's awesome for this devious hardware to exist. And bugs are just a way of life.