Re: [Qemu-devel] [PATCH RFC v6 08/20] dataplane: allow virtio-1 devices

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Thu, Dec 11, 2014 at 02:25:10PM +0100, Cornelia Huck wrote:
> Handle endianness conversion for virtio-1 virtqueues correctly.
> 
> Note that dataplane now needs to be built per-target.
> 
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/block/dataplane/virtio-blk.c               |    4 +-
>  hw/scsi/virtio-scsi-dataplane.c               |    2 +-
>  hw/virtio/Makefile.objs                       |    2 +-
>  hw/virtio/dataplane/Makefile.objs             |    2 +-
>  hw/virtio/dataplane/vring.c                   |   86 ++++++++++++++-----------
>  include/hw/virtio/dataplane/vring-accessors.h |   75 +++++++++++++++++++++
>  include/hw/virtio/dataplane/vring.h           |   14 +---
>  7 files changed, 131 insertions(+), 54 deletions(-)
>  create mode 100644 include/hw/virtio/dataplane/vring-accessors.h

This patch is independent of VIRTIO 1.0 and can be merged separately
(faster).

> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 1222a37..2d8cc15 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -16,7 +16,9 @@
>  #include "qemu/iov.h"
>  #include "qemu/thread.h"
>  #include "qemu/error-report.h"
> +#include "hw/virtio/virtio-access.h"
>  #include "hw/virtio/dataplane/vring.h"
> +#include "hw/virtio/dataplane/vring-accessors.h"

I like your vring-accessors.h approach better than the inline
virtio_ld/st_p() in my patch.  Nice.

> @@ -154,15 +157,18 @@ bool vring_should_notify(VirtIODevice *vdev, Vring *vring)
>  }
>  
>  
> -static int get_desc(Vring *vring, VirtQueueElement *elem,
> +static int get_desc(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,
>                      struct vring_desc *desc)

Since we copy in struct vring_desc anyway, it's cleaner to byteswap the
fields once instead of remembering to do it each time we need to access
a field.  The copy_in_vring_desc() function is one thing I prefer I
about my patch.

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