On Wed, Nov 23, 2022 at 11:46:54AM +0100, Amit Shah wrote: > I think the backward compat concern I have here is that a really old > hypervisor - one that doesn't do virtio-serial-ports yet, will not have > any other messages sent from the host, but the original console setup > messages. > > The is_serial_port() check looks for whether hvc is initialized. It's > possible hvc may not have been initialized when some control message > comes in. I'm assuming you're talking about the is_console_port() check here (apologies I'm not too familiar with the old virtio-serial), in which case I have no problem with. > > If this is correct I think a warning should be emitted here? Not setting the > > value to 1 can exhibit undefined behaviour (at least when interpreting the > > virtIO spec) and it would help hypervisor developers. > > Did you actually run into some issue here? Yes, while developing a hypervisor solution I found that console port setup was unsuccessful when the control messages were involved. I found out later on after reading the qemu and linux source that a value of 1 was needed for all VIRTIO_CONSOLE_CONSOLE_PORT events, which wasn't exactly specified in the spec. Andy _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
