From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tiwei Bie Subject: Re: [PATCH] vhost: fix interrupt suppression for the split ring Date: Mon, 25 Feb 2019 15:06:55 +0800 Message-ID: <20190225070654.GA22485@dpdk-tbie.sh.intel.com> References: <1550823230-16809-1-git-send-email-jiayu.hu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: dev@dpdk.org, maxime.coquelin@redhat.com, stable@dpdk.org To: Jiayu Hu Return-path: Content-Disposition: inline In-Reply-To: <1550823230-16809-1-git-send-email-jiayu.hu@intel.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Fri, Feb 22, 2019 at 04:13:50PM +0800, Jiayu Hu wrote: > The VIRTIO_RING_F_EVENT_IDX feature of split ring might > be broken, as the value of signalled_used is unpredictable > after live migration or start up. This patch fixes it by > using signalled_used_valid. Seems you also need to invalidate the signalled_used in e.g. set_vring_base, as signalled_used may not match last_used_idx anymore e.g. when guest driver is reloaded. > > In addition, this patch makes the VIRTIO_RING_F_EVENT_IDX > implementation of split ring match kernel backend to suppress > more interrupts. > > Fixes: e37ff954405a ("vhost: support virtqueue interrupt/notification suppression") > Cc: stable@dpdk.org > > Signed-off-by: Jiayu Hu > --- > lib/librte_vhost/vhost.h | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h > index fc31796..c4e5e34 100644 > --- a/lib/librte_vhost/vhost.h > +++ b/lib/librte_vhost/vhost.h > @@ -633,16 +633,20 @@ vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq) > if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) { > uint16_t old = vq->signalled_used; > uint16_t new = vq->last_used_idx; > + bool signalled_used_valid = vq->signalled_used_valid; > + > + vq->signalled_used = new; > + vq->signalled_used_valid = true; > > VHOST_LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n", > __func__, > vhost_used_event(vq), > old, new); > - if (vhost_need_event(vhost_used_event(vq), new, old) > - && (vq->callfd >= 0)) { > - vq->signalled_used = vq->last_used_idx; > + > + if ((vhost_need_event(vhost_used_event(vq), new, old) && > + (vq->callfd >= 0)) || > + unlikely(!signalled_used_valid)) > eventfd_write(vq->callfd, (eventfd_t) 1); > - } > } else { > /* Kick the guest if necessary. */ > if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT) > -- > 2.7.4 >