[Qemu-devel] [PATCH-RFC 00/13] vhost-net: preview

[Qemu-devel] [PATCH-RFC 00/13] vhost-net: preview

[Michael S. Tsirkin]

Here's an untested patchset with vhost support for upstream qemu.  Note
that you should not expect performance gains from vhost unless in-kernel
irqchip is enabled (which is not in upstream qemu now).  Since adding
vhost involves quite a bit of infrastructure, I thought it makes sense
to send an RFC already, so that interested parties can review it.  In
particular, command line and help text need to be finalized early to so
that management can start looking on supporting the feature. This patch
has all bits besides migration filled in. Also missing is packet socket
backend: another team is now working on this.


Michael S. Tsirkin (13):
  virtio: export virtqueue structure
  kvm: add API to set ioeventfd
  virtio: add iofd/irqfd support
  virtio-pci: fill in irqfd/queufd support
  syborg_virtio: add irqfd/eventfd support
  s390-virtio: fill in irqfd support
  virtio: move typedef to qemu-common
  net/tap: add interface to get device fd
  tap: add vhost/vhostfd options
  tap: add API to retrieve vhost net header
  vhost net support
  virtio: add status change callback
  virtio-net: connect to vhost net backend

 Makefile.target      |    1 +
 hw/s390-virtio-bus.c |   19 +++
 hw/syborg_virtio.c   |   27 ++++
 hw/vhost.c           |  349 ++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/vhost.h           |   33 +++++
 hw/vhost_net.c       |  145 +++++++++++++++++++++
 hw/vhost_net.h       |   20 +++
 hw/virtio-net.c      |   40 ++++++
 hw/virtio-pci.c      |   32 +++++
 hw/virtio.c          |   31 ++---
 hw/virtio.h          |   23 +++-
 kvm-all.c            |   24 ++++
 kvm.h                |    3 +
 net.c                |    8 +
 net/tap.c            |   43 ++++++
 net/tap.h            |    5 +
 qemu-common.h        |    1 +
 qemu-options.hx      |    4 +-
 18 files changed, 785 insertions(+), 23 deletions(-)
 create mode 100644 hw/vhost.c
 create mode 100644 hw/vhost.h
 create mode 100644 hw/vhost_net.c
 create mode 100644 hw/vhost_net.h

Re: [Qemu-devel] [PATCH-RFC 00/13] vhost-net: preview

[Daniel P. Berrange]

On Mon, Jan 11, 2010 at 07:16:42PM +0200, Michael S. Tsirkin wrote:
> Here's an untested patchset with vhost support for upstream qemu.  Note
> that you should not expect performance gains from vhost unless in-kernel
> irqchip is enabled (which is not in upstream qemu now).  Since adding
> vhost involves quite a bit of infrastructure, I thought it makes sense
> to send an RFC already, so that interested parties can review it.  In
> particular, command line and help text need to be finalized early to so
> that management can start looking on supporting the feature. This patch
> has all bits besides migration filled in. Also missing is packet socket
> backend: another team is now working on this.

Can you clarify a question about migration for me. Is it possible to
live migrate a guest configured with tap + bridge on one machine over
to another where it is launched with vhost + bridge, and vice-versa.
In other words does this vhost support have any guest visible impact
that would cause migraiton compatability problems, or it is purely a
host side optimization like vnet_hdr was ?

Regards,
Daniel
-- 
|: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
|: http://libvirt.org  -o-  http://virt-manager.org  -o-  http://ovirt.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: GnuPG: 7D3B9505  -o-  F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|

Re: [Qemu-devel] [PATCH-RFC 00/13] vhost-net: preview

[Michael S. Tsirkin]

On Mon, Jan 11, 2010 at 08:09:10PM +0000, Daniel P. Berrange wrote:
> On Mon, Jan 11, 2010 at 07:16:42PM +0200, Michael S. Tsirkin wrote:
> > Here's an untested patchset with vhost support for upstream qemu.  Note
> > that you should not expect performance gains from vhost unless in-kernel
> > irqchip is enabled (which is not in upstream qemu now).  Since adding
> > vhost involves quite a bit of infrastructure, I thought it makes sense
> > to send an RFC already, so that interested parties can review it.  In
> > particular, command line and help text need to be finalized early to so
> > that management can start looking on supporting the feature. This patch
> > has all bits besides migration filled in. Also missing is packet socket
> > backend: another team is now working on this.
> 
> Can you clarify a question about migration for me. Is it possible to
> live migrate a guest configured with tap + bridge on one machine over
> to another where it is launched with vhost + bridge, and vice-versa.

Long term, this will be possible without any tweaks.  Currently vhost
does not support mergeable buffers feature which thus needs to be
disabled on both sides for migration to work.  Work is underway to add
this support.

> In other words does this vhost support have any guest visible impact
> that would cause migraiton compatability problems, or it is purely a
> host side optimization like vnet_hdr was ?
> 
> Regards,
> Daniel

vnet_hdr has guest visible impact.

> -- 
> |: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
> |: http://libvirt.org  -o-  http://virt-manager.org  -o-  http://ovirt.org :|
> |: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
> |: GnuPG: 7D3B9505  -o-  F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|