On Fri, May 12, 2017 at 01:21:18PM +0200, Maxime Coquelin wrote: > > > On 05/11/2017 07:33 PM, Michael S. Tsirkin wrote: > > On Thu, May 11, 2017 at 02:32:43PM +0200, Maxime Coquelin wrote: > > > Vhost-kernel backend need to receive IOTLB entries for rings > > > information early, but vhost-user need the same information > > > earlier, before VHOST_USER_SET_VRING_ADDR is sent. > > > > Weird. What does VHOST_USER_SET_VRING_ADDR have to do with it? > > > > According to > > Starting and stopping rings > > in vhost user spec, vhost user does not access > > anything until ring is started and enabled. > > > > > > > This patch also trigger IOTLB miss for all rings informations > > > for robustness, even if in practice these adresses are on the > > > same page. > > Actually, the DPDK vhost-user backend is compliant with the spec, > but when handling VHOST_USER_SET_VRING_ADDR request, it translates the > guest addresses into backend VAs, and check they are valid. I will make the > commit message clearer about this in next revision. > > The check could be done later, for example when the ring are started, > but it wouldn't change the need to trigger a miss at some point.
I think it should be done later, yes. As long as ring is not started addresses should not be interpreted. > Or it could be done in the processing threads, the first time the > addresses are used, but it would add a check for every burst of packets > processed. We don't want that, I agree. > > > > > > Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com> > > > --- > > > hw/virtio/vhost.c | 19 +++++++++++-------- > > > 1 file changed, 11 insertions(+), 8 deletions(-) > > > > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > > index 748e331..817f6d0 100644 > > > --- a/hw/virtio/vhost.c > > > +++ b/hw/virtio/vhost.c > > > @@ -799,7 +799,17 @@ static int vhost_virtqueue_set_addr(struct vhost_dev > > > *dev, > > > .log_guest_addr = vq->used_phys, > > > .flags = enable_log ? (1 << VHOST_VRING_F_LOG) : 0, > > > }; > > > - int r = dev->vhost_ops->vhost_set_vring_addr(dev, &addr); > > > + int r; > > > + > > > + /* Update rings information for IOTLB to work correctly, > > > + * vhost-kernel & vhost-user backends require for this.*/ > > > > Any requirements must be in the spec. Pls add them there. > > Pls fix comment style as you move code. > Sure. > > Thanks, > Maxime
