Re: [PATCH v2 0/7] vhost: support for cross endian guests

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Apr 02, 2015 at 03:16:37PM +0200, Greg Kurz wrote:
> Hi,
> 
> This patchset allows vhost to be used with legacy virtio when guest and host
> have a different endianness. It is a complete rework of my initial post.
> 
> Patches 1 to 5 are preliminary work: we move the endianness check out of all
> memory accessors to separate functions.
> 
> Patch 6 changes the semantics of the accessors so that they have explicit big
> endian support.
> 
> Patch 7 brings the cross-endian feature, with the following changes since v1:
> - conditionnal enablement through a kernel config
> - introduction of a new vhost feature to advertise cross-endian to userspace

I think adding ioctls is sufficient for this, we don't need to burn up a
feature bit.

> The tentative to fix vnet headers was dropped for the moment. As a consequnce,
> vhost_net still fails to work with cross-endian. It will be fixed in another
> patchset I'm currently working on.

I think I'll probably hold off on applying this
patchset until it all actually works.


> ---
> 
> Greg Kurz (7):
>       virtio: introduce virtio_is_little_endian() helper
>       tun: add tun_is_little_endian() helper
>       macvtap: introduce macvtap_is_little_endian() helper
>       vringh: introduce vringh_is_little_endian() helper
>       vhost: introduce vhost_is_little_endian() helper
>       virtio: add explicit big-endian support to memory accessors
>       vhost: feature to set the vring endianness
> 
> 
>  drivers/net/macvtap.c            |   11 +++++++++--
>  drivers/net/tun.c                |   11 +++++++++--
>  drivers/vhost/Kconfig            |   10 ++++++++++
>  drivers/vhost/net.c              |    5 +++++
>  drivers/vhost/scsi.c             |    4 ++++
>  drivers/vhost/test.c             |    4 ++++
>  drivers/vhost/vhost.c            |   19 +++++++++++++++++++
>  drivers/vhost/vhost.h            |   32 +++++++++++++++++++++++++-------
>  include/linux/virtio_byteorder.h |   24 ++++++++++++++----------
>  include/linux/virtio_config.h    |   19 +++++++++++++------
>  include/linux/vringh.h           |   19 +++++++++++++------
>  include/uapi/linux/vhost.h       |   10 ++++++++++
>  12 files changed, 135 insertions(+), 33 deletions(-)
> 
> --
> Greg