Messages in this thread | | | Date | Tue, 25 Aug 2009 20:50:16 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCHv4 2/2] vhost_net: a kernel-level virtio server |
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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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