On 9/20/22 09:45, Liu, Changpeng wrote:
-----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
Ok, it cannot be reverted, as it prevents some undefined
behaviors/crashes.
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.
You can have another thread that sends the call?
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
