Re: virtio balloon: do not call blocking ops when !TASK_RUNNING

On Thu, 26 Feb 2015 09:45:29 +0100
"Michael S. Tsirkin" [off-list ref] wrote:

On Thu, Feb 26, 2015 at 11:50:42AM +1030, Rusty Russell wrote:

quoted

Thomas Huth [off-list ref] writes:

quoted

 Hi all,

with the recent kernel 3.19, I get a kernel warning when I start my
KVM guest on s390 with virtio balloon enabled:

The deeper problem is that virtio_ccw_get_config just silently fails on
OOM.

Same problem with virtio_ccw_reset.
But avoiding kmalloc calls in virtio_ccw_get_config isn't enough I think,
it might still sleep.

It is probably a problem with all calls into the transport that assume
an implementation that cannot fail: If we have a channel I/O backing,
we need to be able to handle things not working.

The only case we need to care about for virtio is probably a -ENODEV
triggered by a hotunplug, though.