Messages in this thread | | | Date | Mon, 8 Oct 2012 22:41:45 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH 0/3] virtio-net: inline header support |
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On Wed, Oct 03, 2012 at 04:14:17PM +0930, Rusty Russell wrote: > "Michael S. Tsirkin" <mst@redhat.com> writes: > > > Thinking about Sasha's patches, we can reduce ring usage > > for virtio net small packets dramatically if we put > > virtio net header inline with the data. > > This can be done for free in case guest net stack allocated > > extra head room for the packet, and I don't see > > why would this have any downsides. > > I've been wanting to do this for the longest time... but... > > > Even though with my recent patches qemu > > no longer requires header to be the first s/g element, > > we need a new feature bit to detect this. > > A trivial qemu patch will be sent separately. > > There's a reason I haven't done this. I really, really dislike "my > implemention isn't broken" feature bits. We could have an infinite > number of them, for each bug in each device. > > So my plan was to tie this assumption to the new PCI layout.
I don't object but old qemu has this limitation for s390 as well, and that's not using PCI, right? So how do we detect new hypervisor there?
-- MST
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