On Thu, 3 Jan 2019 17:08:04 +0100 Cornelia Huck <coh...@redhat.com> 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 <coh...@redhat.com> > --- > 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? Regards, Halil > * @get: read the value of a configuration field > * vdev: the virtio_device > * offset: the offset of the configuration field
