Linux Virtualization - Apr 2009 - [PATCH] virtio-rng: Remove false BUG for spurious callbacks

From: Christian Borntraeger <borntraeger at de.ibm.com>

The virtio-rng drivers checks for spurious callbacks. Since
callbacks can be implemented via shared interrupts (e.g. PCI) this
could lead to guest kernel oopses with lots of virtio devices.

Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
---
 drivers/char/hw_random/virtio-rng.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/char/hw_random/virtio-rng.c
==================================================================---
linux-2.6.orig/drivers/char/hw_random/virtio-rng.c
+++ linux-2.6/drivers/char/hw_random/virtio-rng.c
@@ -37,9 +37,9 @@ static void random_recv_done(struct virt
 {
 	int len;
 
-	/* We never get spurious callbacks. */
+	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
 	if (!vq->vq_ops->get_buf(vq, &len))
-		BUG();
+		return;
 
 	data_left = len / sizeof(random_data[0]);
 	complete(&have_data);

On Thu, 23 Apr 2009, Rusty Russell wrote:
>
> From: Christian Borntraeger <borntraeger at de.ibm.com>
> 
> The virtio-rng drivers checks for spurious callbacks. Since
> callbacks can be implemented via shared interrupts (e.g. PCI) this
> could lead to guest kernel oopses with lots of virtio devices.
> 
> Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
> ---
I really would have liked a sign-off from you too, rusty. I'll take it 
as-is, since it's trivial, but just a note..

		Linus