Hmm. Nevermind.
Please, ignore my previous comments to this patch.
Patch seems compliant to spec, but the spec is not very clear.
Best regards, Ilya Maximets.
On 23.01.2019 16:09, Ilya Maximets wrote:
> On 22.01.2019 20:01, Tiwei Bie wrote:
>> This patch mainly fixed below issues in the packed ring based
>> control vq support in virtio driver:
>>
>> 1. When parsing the used descriptors, we have to track the
>> number of descs that we need to skip;
>> 2. vq->vq_free_cnt was decreased twice for a same desc;
>>
>> Meanwhile, make the function name consistent with other parts.
>>
>> Fixes: ec194c2f1895 ("net/virtio: support packed queue in send command")
>> Fixes: a4270ea4ff79 ("net/virtio: check head desc with correct wrap counter")
>>
>> Signed-off-by: Tiwei Bie <tiwei....@intel.com>
>> ---
>> drivers/net/virtio/virtio_ethdev.c | 62 ++++++++++++++----------------
>> drivers/net/virtio/virtqueue.h | 12 +-----
>> 2 files changed, 31 insertions(+), 43 deletions(-)
>>
>> diff --git a/drivers/net/virtio/virtio_ethdev.c
>> b/drivers/net/virtio/virtio_ethdev.c
>> index ee5a98b7c..a3fe65599 100644
>> --- a/drivers/net/virtio/virtio_ethdev.c
>> +++ b/drivers/net/virtio/virtio_ethdev.c
>> @@ -142,16 +142,17 @@ static const struct rte_virtio_xstats_name_off
>> rte_virtio_txq_stat_strings[] = {
>> struct virtio_hw_internal virtio_hw_internal[RTE_MAX_ETHPORTS];
>>
>> static struct virtio_pmd_ctrl *
>> -virtio_pq_send_command(struct virtnet_ctl *cvq, struct virtio_pmd_ctrl
>> *ctrl,
>> - int *dlen, int pkt_num)
>> +virtio_send_command_packed(struct virtnet_ctl *cvq,
>> + struct virtio_pmd_ctrl *ctrl,
>> + int *dlen, int pkt_num)
>> {
>> struct virtqueue *vq = cvq->vq;
>> int head;
>> struct vring_packed_desc *desc = vq->ring_packed.desc_packed;
>> struct virtio_pmd_ctrl *result;
>> - bool avail_wrap_counter, used_wrap_counter;
>> - uint16_t flags;
>> + bool avail_wrap_counter;
>> int sum = 0;
>> + int nb_descs = 0;
>> int k;
>>
>> /*
>> @@ -162,11 +163,10 @@ virtio_pq_send_command(struct virtnet_ctl *cvq, struct
>> virtio_pmd_ctrl *ctrl,
>> */
>> head = vq->vq_avail_idx;
>> avail_wrap_counter = vq->avail_wrap_counter;
>> - used_wrap_counter = vq->used_wrap_counter;
>> - desc[head].flags = VRING_DESC_F_NEXT;
>> desc[head].addr = cvq->virtio_net_hdr_mem;
>> desc[head].len = sizeof(struct virtio_net_ctrl_hdr);
>> vq->vq_free_cnt--;
>> + nb_descs++;
>> if (++vq->vq_avail_idx >= vq->vq_nentries) {
>> vq->vq_avail_idx -= vq->vq_nentries;
>> vq->avail_wrap_counter ^= 1;
>> @@ -177,55 +177,51 @@ virtio_pq_send_command(struct virtnet_ctl *cvq, struct
>> virtio_pmd_ctrl *ctrl,
>> + sizeof(struct virtio_net_ctrl_hdr)
>> + sizeof(ctrl->status) + sizeof(uint8_t) * sum;
>> desc[vq->vq_avail_idx].len = dlen[k];
>> - flags = VRING_DESC_F_NEXT;
>
> Looks like barriers was badly placed here before this patch.
> Anyway, you need a write barrier here between {addr, len} and flags updates.
>
>> + desc[vq->vq_avail_idx].flags = VRING_DESC_F_NEXT |
>> + VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
>> + VRING_DESC_F_USED(!vq->avail_wrap_counter);
>> sum += dlen[k];
>> vq->vq_free_cnt--;
>> - flags |= VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
>> - VRING_DESC_F_USED(!vq->avail_wrap_counter);
>> - desc[vq->vq_avail_idx].flags = flags;
>> - rte_smp_wmb();
>> - vq->vq_free_cnt--;
>> + nb_descs++;
>> if (++vq->vq_avail_idx >= vq->vq_nentries) {
>> vq->vq_avail_idx -= vq->vq_nentries;
>> vq->avail_wrap_counter ^= 1;
>> }
>> }
>>
>> -
>> desc[vq->vq_avail_idx].addr = cvq->virtio_net_hdr_mem
>> + sizeof(struct virtio_net_ctrl_hdr);
>> desc[vq->vq_avail_idx].len = sizeof(ctrl->status);
>> - flags = VRING_DESC_F_WRITE;
>> - flags |= VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
>> - VRING_DESC_F_USED(!vq->avail_wrap_counter);
>> - desc[vq->vq_avail_idx].flags = flags;
>> - flags = VRING_DESC_F_NEXT;
>> - flags |= VRING_DESC_F_AVAIL(avail_wrap_counter) |
>> - VRING_DESC_F_USED(!avail_wrap_counter);
>> - desc[head].flags = flags;
>> - rte_smp_wmb();
>> -
>
> Same here. We need a write barrier to be sure that {addr, len} written
> before updating flags.
>
> Another way to avoid most of barriers is to work similar to
> 'flush_shadow_used_ring_packed',
> i.e. update all the data in a loop - write barrier - update all the flags.
>
>> + desc[vq->vq_avail_idx].flags = VRING_DESC_F_WRITE |
>> + VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
>> + VRING_DESC_F_USED(!vq->avail_wrap_counter);
>> vq->vq_free_cnt--;
>> + nb_descs++;
>> if (++vq->vq_avail_idx >= vq->vq_nentries) {
>> vq->vq_avail_idx -= vq->vq_nentries;
>> vq->avail_wrap_counter ^= 1;
>> }
>>
>> + virtio_wmb(vq->hw->weak_barriers);
>> + desc[head].flags = VRING_DESC_F_NEXT |
>> + VRING_DESC_F_AVAIL(avail_wrap_counter) |
>> + VRING_DESC_F_USED(!avail_wrap_counter);
>> +
>> + virtio_wmb(vq->hw->weak_barriers);
>> virtqueue_notify(vq);
>>
>> /* wait for used descriptors in virtqueue */
>> - do {
>> - rte_rmb();
>> + while (!desc_is_used(&desc[head], vq))
>> usleep(100);
>> - } while (!__desc_is_used(&desc[head], used_wrap_counter));
>> +
>> + virtio_rmb(vq->hw->weak_barriers);
>>
>> /* now get used descriptors */
>> - while (desc_is_used(&desc[vq->vq_used_cons_idx], vq)) {
>> - vq->vq_free_cnt++;
>> - if (++vq->vq_used_cons_idx >= vq->vq_nentries) {
>> - vq->vq_used_cons_idx -= vq->vq_nentries;
>> - vq->used_wrap_counter ^= 1;
>> - }
>> + vq->vq_free_cnt += nb_descs;
>> + vq->vq_used_cons_idx += nb_descs;
>> + if (vq->vq_used_cons_idx >= vq->vq_nentries) {
>> + vq->vq_used_cons_idx -= vq->vq_nentries;
>> + vq->used_wrap_counter ^= 1;
>> }
>>
>> result = cvq->virtio_net_hdr_mz->addr;
>> @@ -266,7 +262,7 @@ virtio_send_command(struct virtnet_ctl *cvq, struct
>> virtio_pmd_ctrl *ctrl,
>> sizeof(struct virtio_pmd_ctrl));
>>
>> if (vtpci_packed_queue(vq->hw)) {
>> - result = virtio_pq_send_command(cvq, ctrl, dlen, pkt_num);
>> + result = virtio_send_command_packed(cvq, ctrl, dlen, pkt_num);
>> goto out_unlock;
>> }
>>
>> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
>> index 7fcde5643..ca9d8e6e3 100644
>> --- a/drivers/net/virtio/virtqueue.h
>> +++ b/drivers/net/virtio/virtqueue.h
>> @@ -281,7 +281,7 @@ struct virtio_tx_region {
>> };
>>
>> static inline int
>> -__desc_is_used(struct vring_packed_desc *desc, bool wrap_counter)
>> +desc_is_used(struct vring_packed_desc *desc, struct virtqueue *vq)
>> {
>> uint16_t used, avail, flags;
>>
>> @@ -289,16 +289,9 @@ __desc_is_used(struct vring_packed_desc *desc, bool
>> wrap_counter)
>> used = !!(flags & VRING_DESC_F_USED(1));
>> avail = !!(flags & VRING_DESC_F_AVAIL(1));
>>
>> - return avail == used && used == wrap_counter;
>> + return avail == used && used == vq->used_wrap_counter;
>> }
>>
>> -static inline int
>> -desc_is_used(struct vring_packed_desc *desc, struct virtqueue *vq)
>> -{
>> - return __desc_is_used(desc, vq->used_wrap_counter);
>> -}
>> -
>> -
>> static inline void
>> vring_desc_init_packed(struct virtqueue *vq, int n)
>> {
>> @@ -354,7 +347,6 @@ virtqueue_enable_intr_packed(struct virtqueue *vq)
>> {
>> uint16_t *event_flags = &vq->ring_packed.driver_event->desc_event_flags;
>>
>> -
>> if (vq->event_flags_shadow == RING_EVENT_FLAGS_DISABLE) {
>> virtio_wmb(vq->hw->weak_barriers);
>> vq->event_flags_shadow = RING_EVENT_FLAGS_ENABLE;
>>
