RE: [PATCH v4 1/2] vhost: introduce DMA vchannel unconfiguration

["Ding, Xuan" <xuan.ding@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, October 13, 2022 4:02 PM
> To: Ding, Xuan <xuan.ding@intel.com>; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; He, Xingguang
> <xingguang.he@intel.com>; Yang, YvonneX <yvonnex.yang@intel.com>;
> Jiang, Cheng1 <cheng1.jiang@intel.com>; Wang, YuanX
> <yuanx.wang@intel.com>; Ma, WenwuX <wenwux.ma@intel.com>
> Subject: Re: [PATCH v4 1/2] vhost: introduce DMA vchannel unconfiguration
> 
> 
> 
> On 10/13/22 08:40, xuan.ding@intel.com wrote:
> > From: Xuan Ding <xuan.ding@intel.com>
> >
> > Add a new API rte_vhost_async_dma_unconfigure() to unconfigure DMA
> > vchannels in vhost async data path. Lock protection are also added to
> > protect DMA vchannels configuration and unconfiguration from
> > concurrent calls.
> >
> > Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> > ---
> >   doc/guides/prog_guide/vhost_lib.rst    |  6 +++
> >   doc/guides/rel_notes/release_22_11.rst |  4 ++
> >   lib/vhost/rte_vhost_async.h            | 18 +++++++
> >   lib/vhost/version.map                  |  3 ++
> >   lib/vhost/vhost.c                      | 69 ++++++++++++++++++++++++--
> >   5 files changed, 95 insertions(+), 5 deletions(-)
> >
> > diff --git a/doc/guides/prog_guide/vhost_lib.rst
> > b/doc/guides/prog_guide/vhost_lib.rst
> > index bad4d819e1..d3cef978d0 100644
> > --- a/doc/guides/prog_guide/vhost_lib.rst
> > +++ b/doc/guides/prog_guide/vhost_lib.rst
> > @@ -323,6 +323,12 @@ The following is an overview of some key Vhost
> API functions:
> >     Get device type of vDPA device, such as VDPA_DEVICE_TYPE_NET,
> >     VDPA_DEVICE_TYPE_BLK.
> >
> > +* ``rte_vhost_async_dma_unconfigure(dma_id, vchan_id)``
> > +
> > +  Clean DMA vChannels finished to use. This function needs to  be
> > + called after the deregistration of async DMA vchannel  has been
> > + finished.
> > +
> >   Vhost-user Implementations
> >   --------------------------
> >
> > diff --git a/doc/guides/rel_notes/release_22_11.rst
> > b/doc/guides/rel_notes/release_22_11.rst
> > index 2da8bc9661..3be150122c 100644
> > --- a/doc/guides/rel_notes/release_22_11.rst
> > +++ b/doc/guides/rel_notes/release_22_11.rst
> > @@ -236,6 +236,10 @@ New Features
> >
> >        strings $dpdk_binary_or_driver | sed -n 's/^PMD_INFO_STRING= //p'
> >
> > +* **Added DMA vChannel unconfiguration for async vhost.**
> > +
> > +  * Added support to unconfigure DMA vChannels that have been
> unregistered.
> > +
> >
> >   Removed Items
> >   -------------
> > diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
> > index 1db2a10124..6ee4f7258d 100644
> > --- a/lib/vhost/rte_vhost_async.h
> > +++ b/lib/vhost/rte_vhost_async.h
> > @@ -266,6 +266,24 @@ rte_vhost_async_try_dequeue_burst(int vid,
> uint16_t queue_id,
> >   	struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t
> count,
> >   	int *nr_inflight, int16_t dma_id, uint16_t vchan_id);
> >
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change, or be removed, without prior
> notice.
> > + *
> > + * Unconfigure DMA vChannels in asynchronous data path.
> > + * This function should be called after the DMA vChannel has been
> unregistered.
> > + *
> > + * @param dma_id
> > + *  the identifier of DMA device
> > + * @param vchan_id
> > + *  the identifier of virtual DMA channel
> > + * @return
> > + *  0 on success, and -1 on failure
> > + */
> > +__rte_experimental
> > +int
> > +rte_vhost_async_dma_unconfigure(int16_t dma_id, uint16_t vchan_id);
> > +
> >   #ifdef __cplusplus
> >   }
> >   #endif
> > diff --git a/lib/vhost/version.map b/lib/vhost/version.map index
> > 7a00b65740..0b61870870 100644
> > --- a/lib/vhost/version.map
> > +++ b/lib/vhost/version.map
> > @@ -94,6 +94,9 @@ EXPERIMENTAL {
> >   	rte_vhost_async_try_dequeue_burst;
> >   	rte_vhost_driver_get_vdpa_dev_type;
> >   	rte_vhost_clear_queue;
> > +
> > +	# added in 22.11
> > +	rte_vhost_async_dma_unconfigure;
> >   };
> >
> >   INTERNAL {
> > diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c index
> > 8740aa2788..9fbc56229a 100644
> > --- a/lib/vhost/vhost.c
> > +++ b/lib/vhost/vhost.c
> > @@ -23,6 +23,7 @@
> >
> >   struct virtio_net *vhost_devices[RTE_MAX_VHOST_DEVICE];
> >   pthread_mutex_t vhost_dev_lock = PTHREAD_MUTEX_INITIALIZER;
> > +static rte_spinlock_t vhost_dma_lock = RTE_SPINLOCK_INITIALIZER;
> 
> I think a mutex would be more appropiate.

Thanks for your suggestion.
Maybe mutex is more efficient, I will switch to mutex in next version.

Regards,
Xuan

> 
> Thanks,
> Maxime