On Thu, 26 Feb 2015 11:50:42 +1030 Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx> writes: > > 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. > > Neither get_config nor set_config are expected to fail. It is a problem that we cannot relay failures back to the caller: not only for the memory allocations. We need to do channel I/O, and any channel I/O can fail. For our virtio case, we don't have to deal with the failures that may happen on real hardware (like path failures), but what can happen is a hotunplug, which means we cannot talk to the device anymore from one moment to the other. > > Cornelia, I think ccw and config_area should be allocated inside vcdev. > You could either use pointers, or simply allocate vcdev with GDP_DMA. > > This would avoid the kmalloc inside these calls. I can certainly look into that, but I'm not sure it's worth it. We still have to deal with possible failures from doing channel I/O. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
