On Monday 10 August 2009 20:10:44 Michael S. Tsirkin wrote: > On Mon, Aug 10, 2009 at 09:51:18PM +0200, Arnd Bergmann wrote: > > what is the difference between vhost_net_reset_owner(n) > > and vhost_net_set_socket(n, -1)? > > set socket to -1 will only stop the device. > > reset owner will let another process take over the device. > It also needs to reset all parameters to make it safe for that > other process, so in particular the device is stopped. ok > I tried explaining this in the header vhost.h - does the comment > there help, or do I need to clarify it? No, I just didn't get there yet. > I had the impression that if there's no compat_ioctl, > unlocked_ioctl will get called automatically. No? It will issue a kernel warning but not call unlocked_ioctl, so you need either a compat_ioctl method or list the numbers in fs/compat_ioctl.c, which I try to avoid. > > Why do you need a kernel thread here? If the data transfer functions > > all get called from a guest intercept, shouldn't you already be > > in the right mm? > > several reasons :) > - I get called under lock, so can't block > - eventfd can be passed to another process, and I won't be in guest context at all > - this also gets called outside guest context from socket poll > - vcpu is blocked while it's doing i/o. it is better to free it up > as all the packet copying might take a while Ok. > > I guess that this is where one could plug into macvlan directly, using > > sock_alloc_send_skb/memcpy_fromiovec/dev_queue_xmit directly, > > instead of filling a msghdr for each, if we want to combine this > > with the work I did on that. > > quite possibly. Or one can just bind a raw socket to macvlan :) Right, that works as well, but may get more complicated once we try to add zero-copy or other optimizations. Arnd <>< -- 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
