Re: [dpdk-dev] [PATCH] vhost: fix vhost interrupt support

[Maxime Coquelin]

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?

  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])