Re: [dpdk-dev] [PATCH] examples/vhost_scsi: drop unimplemented EVENT_IDX feature bit

["Liu, Changpeng" <changpeng.liu@intel.com>]

> -----Original Message-----
> From: Stefan Hajnoczi [mailto:stefanha@redhat.com]
> Sent: Thursday, February 1, 2018 1:48 AM
> To: dev@dpdk.org
> Cc: Chen, Junjie J <junjie.j.chen@intel.com>; Yuanhan Liu <yliu@fridaylinux.org>;
> Liu, Changpeng <changpeng.liu@intel.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>; Stefan Hajnoczi <stefanha@redhat.com>
> Subject: [PATCH] examples/vhost_scsi: drop unimplemented EVENT_IDX feature
> bit
> 
> The vhost_scsi example application negotiates the
> VIRTIO_RING_F_EVENT_IDX feature bit but does not honor it when accessing
> vrings.
> 
> In particular, commit e37ff954405addb8ea422426a2d162d00dcad196 ("vhost:
> support virtqueue interrupt/notification suppression") broke vring call
> because vq->last_used_idx is never updated by vhost_scsi.  The
> vq->last_used_idx field is not even available via the librte_vhost
> public API, so VIRTIO_RING_F_EVENT_IDX is currently only usable by the
> built-in virtio_net.c driver in librte_vhost.
> 
> This patch drops VIRTIO_RING_F_EVENT_IDX from vhost_scsi so that vring
> call works again.
> 
> Cc: Changpeng Liu <changpeng.liu@intel.com>
> Cc: Junjie Chen <junjie.j.chen@intel.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  examples/vhost_scsi/vhost_scsi.c | 1 -
>  1 file changed, 1 deletion(-)

Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
> 
> diff --git a/examples/vhost_scsi/vhost_scsi.c b/examples/vhost_scsi/vhost_scsi.c
> index da01ad378..3cb4383e9 100644
> --- a/examples/vhost_scsi/vhost_scsi.c
> +++ b/examples/vhost_scsi/vhost_scsi.c
> @@ -21,7 +21,6 @@
>  #include "scsi_spec.h"
> 
>  #define VIRTIO_SCSI_FEATURES ((1 << VIRTIO_F_NOTIFY_ON_EMPTY) |\
> -			      (1 << VIRTIO_RING_F_EVENT_IDX) |\
>  			      (1 << VIRTIO_SCSI_F_INOUT) |\
>  			      (1 << VIRTIO_SCSI_F_CHANGE))
> 
> --
> 2.14.3