On Thu, 3 Jan 2019 18:28:49 +0100 Halil Pasic <pasic@xxxxxxxxxxxxx> wrote: > On Thu, 3 Jan 2019 17:08:04 +0100 > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > > > Some transports (e.g. virtio-ccw) implement virtio operations that > > seem to be a simple read/write as something more involved that > > cannot be done from an atomic context. > > > > Give at least a hint about that. > > > > Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx> > > --- > > include/linux/virtio_config.h | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > > index 7087ef946ba7..987b6491b946 100644 > > --- a/include/linux/virtio_config.h > > +++ b/include/linux/virtio_config.h > > @@ -12,6 +12,11 @@ struct irq_affinity; > > > > /** > > * virtio_config_ops - operations for configuring a virtio device > > + * Note: Do not assume that a transport implements all of the operations > > + * getting/setting a value as a simple read/write! Generally speaking, > > + * any of @get/@set, @get_status/@set_status, or @get_features/ > > + * @finalize_features are NOT safe to be called from an atomic > > + * context. > > I think the only exception is @bus_name (and maybe @generation, I don't > know) because it does not have to 'speak' with the hypervisor. If a > transport operation has to 'speak' with the hypervisor, we do it by > making it interpret a channel program. That means not safe to be called > form atomic context. Or am I missing something? I explicitly singled out the listed callbacks because they read/write a value and there might be more to them than meets the eye. I would assume that nobody expects calling e.g. find_vqs (allocating queues) from an atomic context to be a good idea :) Maybe I should do s/Generally speaking/In particular/ ? That said, it's only a hint; we should add might_sleep as well to interfaces where it makes sense. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
