Hi Maxime,
On Mon, Sep 10, 2018 at 09:22:00AM +0200, Maxime Coquelin wrote:
> Hi Tiwei,
>
> On 09/05/2018 01:55 AM, Tiwei Bie wrote:
> > When VIRTIO_RING_F_EVENT_IDX is negotiated, we need to
> > update the avail event to enable the notification.
> >
> > Fixes: 3f8ff12821e4 ("vhost: support interrupt mode")
> > Cc: sta...@dpdk.org
> >
> > Signed-off-by: Tiwei Bie <tiwei....@intel.com>
> > ---
> > lib/librte_vhost/Makefile | 1 +
> > lib/librte_vhost/vhost.c | 18 ++++++++++++------
> > lib/librte_vhost/vhost.h | 2 ++
> > 3 files changed, 15 insertions(+), 6 deletions(-)
> >
> > diff --git a/lib/librte_vhost/Makefile b/lib/librte_vhost/Makefile
> > index de431fbb7..531cf4832 100644
> > --- a/lib/librte_vhost/Makefile
> > +++ b/lib/librte_vhost/Makefile
> > @@ -13,6 +13,7 @@ LIBABIVER := 4
> > CFLAGS += -DALLOW_EXPERIMENTAL_API
> > CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR) -O3 -D_FILE_OFFSET_BITS=64
> > CFLAGS += -I vhost_user
> > +CFLAGS += -fno-strict-aliasing
>
> I'm not clear why this is needed looking at the code below,
> could you please explain?
Without this, we will get below build error:
lib/librte_vhost/vhost.c: In function ‘vhost_enable_notify_split’:
lib/librte_vhost/vhost.h:656:4: error: dereferencing type-punned pointer will
break strict-aliasing rules [-Werror=strict-aliasing]
(*(volatile uint16_t*)&(vr)->used->ring[(vr)->size])
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lib/librte_vhost/vhost.c:659:4: note: in expansion of macro ‘vhost_avail_event’
vhost_avail_event(vq) = vq->last_avail_idx;
^~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
>
> > LDLIBS += -lpthread
> > ifeq ($(CONFIG_RTE_LIBRTE_VHOST_NUMA),y)
> > diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> > index 3c9be10a0..88b1781d5 100644
> > --- a/lib/librte_vhost/vhost.c
> > +++ b/lib/librte_vhost/vhost.c
> > @@ -646,12 +646,18 @@ rte_vhost_avail_entries(int vid, uint16_t queue_id)
> > }
> > static inline void
> > -vhost_enable_notify_split(struct vhost_virtqueue *vq, int enable)
> > +vhost_enable_notify_split(struct virtio_net *dev,
> > + struct vhost_virtqueue *vq, int enable)
> > {
> > - if (enable)
> > - vq->used->flags &= ~VRING_USED_F_NO_NOTIFY;
> > - else
> > - vq->used->flags |= VRING_USED_F_NO_NOTIFY;
> > + if (!(dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX))) {
> > + if (enable)
> > + vq->used->flags &= ~VRING_USED_F_NO_NOTIFY;
> > + else
> > + vq->used->flags |= VRING_USED_F_NO_NOTIFY;
> > + } else {
> > + if (enable)
> > + vhost_avail_event(vq) = vq->last_avail_idx;
> > + }
> > }
> > static inline void
> > @@ -689,7 +695,7 @@ rte_vhost_enable_guest_notification(int vid, uint16_t
> > queue_id, int enable)
> > if (vq_is_packed(dev))
> > vhost_enable_notify_packed(dev, vq, enable);
> > else
> > - vhost_enable_notify_split(vq, enable);
> > + vhost_enable_notify_split(dev, vq, enable);
> > return 0;
> > }
> > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> > index 760a09c0d..25ffd7614 100644
> > --- a/lib/librte_vhost/vhost.h
> > +++ b/lib/librte_vhost/vhost.h
> > @@ -648,6 +648,8 @@ vhost_iova_to_vva(struct virtio_net *dev, struct
> > vhost_virtqueue *vq,
> > return __vhost_iova_to_vva(dev, vq, iova, len, perm);
> > }
> > +#define vhost_avail_event(vr) \
> > + (*(volatile uint16_t*)&(vr)->used->ring[(vr)->size])
> > #define vhost_used_event(vr) \
> > (*(volatile uint16_t*)&(vr)->avail->ring[(vr)->size])
> >
