[PATCH] virtio: Remove virtio devices on device_shutdown()

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Hongyu reported a hang on kexec in a VM. QEMU reported invalid memory
accesses during the hang.

	Invalid read at addr 0x102877002, size 2, region '(null)', reason: rejected
	Invalid write at addr 0x102877A44, size 2, region '(null)', reason: rejected
	...

It was traced down to virtio-console. Kexec works fine if virtio-console
is not in use.

Looks like virtio-console continues to write to the MMIO even after
underlying virtio-pci device is removed.

The problem can be mitigated by removing all virtio devices on virtio
bus shutdown.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Hongyu Ning <hongyu.ning@linux.intel.com>
---
 drivers/virtio/virtio.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a9b93e99c23a..6c2f908eb22c 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -356,6 +356,15 @@ static void virtio_dev_remove(struct device *_d)
 	of_node_put(dev->dev.of_node);
 }
 
+static void virtio_dev_shutdown(struct device *_d)
+{
+	struct virtio_device *dev = dev_to_virtio(_d);
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+
+	if (drv && drv->remove)
+		drv->remove(dev);
+}
+
 static const struct bus_type virtio_bus = {
 	.name  = "virtio",
 	.match = virtio_dev_match,
@@ -363,6 +372,7 @@ static const struct bus_type virtio_bus = {
 	.uevent = virtio_uevent,
 	.probe = virtio_dev_probe,
 	.remove = virtio_dev_remove,
+	.shutdown = virtio_dev_shutdown,
 };
 
 int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
-- 
2.43.0