On 9/10/2018 8:36 AM, Tiwei Bie wrote:
> 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
>
Getting this error with meson build system, since "-fno-strict-aliasing" is not
added to meson build file. BUT instead of disabling compiler warning,
first element of the "struct vring_used_elem ring[0]" is "uint32_t id;", so it
should be accessed as uint32_t. What about following:
#define vhost_avail_event(vr) \
- (*(volatile uint16_t*)&(vr)->used->ring[(vr)->size])
+ (*(volatile uint32_t*)&(vr)->used->ring[(vr)->size])
And for "vhost_avail_event(vq) = vq->last_avail_idx;", "last_avail_idx" is
uint16_t, so assigning from uint16_t to uint32_t should be ok too.
If above works for you please send a patch for update also removing
"-fno-strict-aliasing", this can be rebased on existing patch.
If not works, please at least send a patch to add flag to meson build file
Thanks,
ferruh
>>
>>> 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])
>>>
