Re: [dpdk-dev] [PATCH v5 3/5] vhost: handle memory hotplug for async vhost

["Hu, Jiayu" <jiayu.hu@intel.com>]

> -----Original Message-----
> From: Xia, Chenbo <chenbo.xia@intel.com>
> Sent: Monday, July 19, 2021 1:19 PM
> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; maxime.coquelin@redhat.com;
> Hu, Jiayu <jiayu.hu@intel.com>
> Cc: dev@dpdk.org; Yang, YvonneX <yvonnex.yang@intel.com>
> Subject: RE: [PATCH v5 3/5] vhost: handle memory hotplug for async vhost
> 
> Hi Cheng & Jiayu,
> 
> > -----Original Message-----
> > From: Jiang, Cheng1 <cheng1.jiang@intel.com>
> > Sent: Friday, July 16, 2021 3:25 PM
> > To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> > Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Yang, YvonneX
> > <yvonnex.yang@intel.com>
> > Subject: [PATCH v5 3/5] vhost: handle memory hotplug for async vhost
> >
> > From: Jiayu Hu <jiayu.hu@intel.com>
> >
> > When the guest memory is hotplugged, the vhost application which
> > enables DMA acceleration must stop DMA transfers before the vhost
> > re-maps the guest memory.
> >
> > This patch is to notify the vhost application of stopping DMA
> > transfers.
> >
> > Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> > ---
> >  lib/vhost/vhost_user.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c index
> > 031c578e54..39e8432d1c 100644
> > --- a/lib/vhost/vhost_user.c
> > +++ b/lib/vhost/vhost_user.c
> > @@ -1275,6 +1275,15 @@ vhost_user_set_mem_table(struct virtio_net
> > **pdev, struct VhostUserMsg *msg,
> >  				vdpa_dev->ops->dev_close(dev->vid);
> >  			dev->flags &= ~VIRTIO_DEV_VDPA_CONFIGURED;
> >  		}
> > +
> > +		/* notify the backend application to stop DMA transfers */
> 
> Backend application -> vhost application
> 
> > +		if (dev->async_copy && dev->notify_ops-
> >vring_state_changed) {
> > +			for (i = 0; i < dev->nr_vring; i++) {
> > +				dev->notify_ops->vring_state_changed(dev-
> >vid,
> > +						i, 0);
> > +			}
> > +		}
> > +
> 
> In this case, I think app will never know the vring is enabled again with
> memory table updated.

I will add enable notification in set_mem_table.

Thanks,
Jiayu
> 
> Thanks,
> Chenbo
> 
> >  		free_mem_region(dev);
> >  		rte_free(dev->mem);
> >  		dev->mem = NULL;
> > --
> > 2.29.2
>