> -----Original Message-----
> From: Maxime Coquelin <maxime.coque...@redhat.com>
> Sent: Tuesday, September 20, 2022 3:35 PM
> To: Liu, Changpeng <changpeng....@intel.com>; dev@dpdk.org
> Cc: Xia, Chenbo <chenbo....@intel.com>
> Subject: Re: [PATCH] vhost: use try_lock in rte_vhost_vring_call
>
>
>
> On 9/20/22 09:29, Liu, Changpeng wrote:
> > Hi Maxime,
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin <maxime.coque...@redhat.com>
> >> Sent: Tuesday, September 20, 2022 3:19 PM
> >> To: Liu, Changpeng <changpeng....@intel.com>; dev@dpdk.org
> >> Cc: Xia, Chenbo <chenbo....@intel.com>
> >> Subject: Re: [PATCH] vhost: use try_lock in rte_vhost_vring_call
> >>
> >>
> >>
> >> On 9/6/22 04:22, Changpeng Liu wrote:
> >>> Note that this function is in data path, so the thread context
> >>> may not same as socket messages processing context, by using
> >>> try_lock here, users can have another try in case of VQ's access
> >>> lock is held by `vhost-events` thread.
> >>>
> >>> Signed-off-by: Changpeng Liu <changpeng....@intel.com>
> >>> ---
> >>> lib/vhost/vhost.c | 6 +++++-
> >>> 1 file changed, 5 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> >>> index 60cb05a0ff..072d2acb7b 100644
> >>> --- a/lib/vhost/vhost.c
> >>> +++ b/lib/vhost/vhost.c
> >>> @@ -1329,7 +1329,11 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
> >>> if (!vq)
> >>> return -1;
> >>>
> >>> - rte_spinlock_lock(&vq->access_lock);
> >>> + if (!rte_spinlock_trylock(&vq->access_lock)) {
> >>> + VHOST_LOG_CONFIG(dev->ifname, DEBUG,
> >>> + "failed to kick guest, virtqueue busy.\n");
> >>> + return -1;
> >>> + }
> >>>
> >>> if (vq_is_packed(dev))
> >>> vhost_vring_call_packed(dev, vq);
> >>
> >> I think that's problematic, because it will break other applications
> >> that currently rely on the API to block until the call is done.
> >>
> >> Just some internal DPDK usage of this API:
> >> ./drivers/vdpa/ifc/ifcvf_vdpa.c:871:
> >> rte_vhost_vring_call(internal->vid,
> >> qid);
> >> ./examples/vhost/virtio_net.c:236: rte_vhost_vring_call(dev->vid,
> >> queue_id);
> >> ./examples/vhost/virtio_net.c:446: rte_vhost_vring_call(dev->vid,
> >> queue_id);
> >> ./examples/vhost_blk/vhost_blk.c:99:
> >> rte_vhost_vring_call(task->ctrlr->vid, vq->id);
> >> ./examples/vhost_blk/vhost_blk.c:134:
> >> rte_vhost_vring_call(task->ctrlr->vid, vq->id);
> >>
> >> This change will break all the above uses.
> >>
> >> And that's not counting external projects.
> >>
> >> ou should better introduce a new API that does not block.
> > Could you add a new API to do this?
> >
> > I think we can use the new API in SPDK as a workaround, note that SPDK
> > project
> is blocked for
> > a while which can't be used with DPDK 22.05 or newer.
>
> DPDK v22.05?
> What is the commit introducing the regression?
Here is the commit introducing this issue
c5736998305d ("vhost: fix missing virtqueue lock protection")
Bugzilla ID: 1015
>
> Note that if we introduce a new API, it won't be backported to stable
> branches.
I understand, but do we have better idea in short time? we're planning
to release SPDK 22.09 recently.
>
>
> > Vhost-blk and scsi devices are not same with vhost-net, we need to cover
> SeaBIOS and VM
> > cases, so we need to start processing vrings after 1 vring is ready.
> >>
> >> Regards,
> >> Maxime
> >
