On Mon, Nov 17, 2014 at 11:20:48AM +0100, Cornelia Huck wrote: > On Mon, 17 Nov 2014 12:11:39 +0200 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > On Mon, Nov 17, 2014 at 10:44:30AM +0100, Cornelia Huck wrote: > > > On Mon, 17 Nov 2014 11:37:01 +0200 > > > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > > > > On Mon, Nov 17, 2014 at 05:17:17PM +0800, Jason Wang wrote: > > > > > Buggy host may advertised buggy host features (a usual case is that > > > > > host > > > > > advertise a feature whose dependencies were missed). In this case, > > > > > driver > > > > > should detect and disable the buggy features by itself. > > > > > > > > > > This patch introduces driver specific sanitize_features() method > > > > > which is > > > > > called just before features finalizing to detect and disable buggy > > > > > features > > > > > advertised by host. > > > > > > > > > > Virtio-net will be the first user. > > > > > > > > > > Cc: Rusty Russell <ru...@rustcorp.com.au> > > > > > Cc: Michael S. Tsirkin <m...@redhat.com> > > > > > Cc: Cornelia Huck <cornelia.h...@de.ibm.com> > > > > > Cc: Wanlong Gao <gaowanl...@cn.fujitsu.com> > > > > > Signed-off-by: Jason Wang <jasow...@redhat.com> > > > > > > > > Hmm this conflicts with virtio 1.0 work: we drop > > > > features as bitmap there. > > > > > > But that's an implementation detail, no? We'll still need a way for the > > > driver to sanitize features, and I think this interface works just fine. > > > > Now that you mention it, I don't think we do. > > > > The spec is quite explicit that devices must not expose invalid > > combinations of features. > > Unfortunately, this does not ensure that there won't be buggy > hypervisors out there, just as there's buggy hardware floating around. > > > > > Admittedly, BUG_ON isn't very friendly to hypervisors. > > > > But e.g. failing probe seems better than trying to work around > > hypervisor bugs - otherwise we'll be stuck maintaining compatibility > > with hypervisors forever. > > Good point. Failing probe is still much better than hitting BUG_ONs. > > We'll still need a driver callback, though, that can return an error on > bogus feature bit combinations.
Why bother? Just check features at start of probe, and return an error. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
