On Tue, Aug 25, 2009 at 09:40:40PM +0930, Rusty Russell wrote:
> > + u32 __user *featurep = argp;
> > + int __user *fdp = argp;
> > + u32 features;
> > + int fd, r;
> > + switch (ioctl) {
> > + case VHOST_NET_SET_SOCKET:
> > + r = get_user(fd, fdp);
> > + if (r < 0)
> > + return r;
> > + return vhost_net_set_socket(n, fd);
> > + case VHOST_GET_FEATURES:
> > + /* No features for now */
> > + features = 0;
> > + return put_user(features, featurep);
>
> We may well get more than 32 feature bits, at least for virtio_net, which will
> force us to do some trickery in virtio_pci.
Unlike PCI, if we ever run out of bits we can just
add FEATURES_EXTENDED ioctl, no need for trickery.
> I'd like to avoid that here,
> though it's kind of ugly. We'd need VHOST_GET_FEATURES (and ACK) to take a
> struct like:
>
> u32 feature_size;
> u32 features[];
Thinking about this proposal some more, how will the guest
determine the size to supply the GET_FEATURES ioctl?
Since we are a bit tight in 32 bit space already,
let's just use a 64 bit integer and be done with it?
Right?
--
MST
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