Re: A new direction for vmchannel?

Anthony Liguori
2009-01-23T17:37:50Z

Chris Wright wrote:
> * Anthony Liguori (aliguori@us.ibm.com) wrote:
>
>> The userspace configuration aspects of the current implementation of
>> vmchannel are pretty annoying. Moreover, we would like to make use of
>> something like vmchannel in a kernel driver and I fear that it's going
>> to be difficult to do that.
>>
>
> What's the use for vmchannel from kernel driver?
>

Well, it doesn't exactly have to be vmchannel, but the desire is to have
the management tools to be able to communicate directly with a kernel
driver. We could certainly just use virtio and route it through QEMU to
the management tool. It would be useful to just use vmchannel though.

>> Thoughts?
>>
>
> Heh, works for me ;-) Last time I suggested an fs it got shot down due to
> the burden it puts on the guest implementation (notably windows and
> other guests and ease of adding a new fs implementation).
>
> Doesn't directly solve addressing (IOW, easy to do with hierarchical
> namespace, but if vmchannel ever talks guest-to-guest...). Clearly not
> a huge issue.
>
> Should handle the reliable messaging bit (one big push for using tcp),
> and has advantage of being a structured protocol.
>
> Has the similar ABI issue that we see in Linux with sysfs, namely it's
> easy to screw up...but that is manageable.
>
> BTW, what ever happened to just using a serial device (granted needs
> some protocol layered on top...)?
>

I think you end up having a lot of the same issues with respect to
making it transparent to the guest. You could still do 9p over serial
and still use a synthetic file system in the guest. In fact, this is a
pretty reasonable thing to do for older kernel guests and even Windows.

Regards,

Anthony Liguori

> thanks,
> -chris
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>