[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Re: [PATCH-RFC 13/13] virtio-net: connect to vhost net
Michael S. Tsirkin
Re: [Qemu-devel] Re: [PATCH-RFC 13/13] virtio-net: connect to vhost net backend
Wed, 24 Feb 2010 14:40:16 +0200
On Wed, Feb 24, 2010 at 12:26:53PM +0000, Paul Brook wrote:
> > > If we do have a software
> > > fallback then the feature bit is just for backwards compatibility, and
> > > should be enabled unconditionally (on current machine types).
> > Software fallback might turn out to be slower than disabling the feature
> > in the guest. For example, and extra pass over packet might cause extra CPU
> > cache thrashing. In that case, it's not obvious whether enabling it
> > unconditionally will turn out to be a good idea. But we'll have to have
> > that code to be able to tell.
> IMO once you accept that these things can change, consistency is more
> important than trying to guess what the "best" option may be.
Yes, SW fallback might be nice to have. What's important is likely to
depend on specific user.
> Starting qemu on machine A and migrating to machine B should give the same
> guest environment as starting on machine B.
So currently, the way we try to ensure this is by checking feature bits
against the list supported by backend, and failing migration if there's
Re: [Qemu-devel] Re: [PATCH-RFC 13/13] virtio-net: connect to vhost net backend, Anthony Liguori, 2010/02/24