On Mon, Mar 24, 2025 at 3:00 PM Sahil Siddiq <icegambi...@gmail.com> wrote: > > Implement the insertion of available buffers in the descriptor area of > packed shadow virtqueues. It takes into account descriptor chains, but > does not consider indirect descriptors. > > Enable the packed SVQ to forward the descriptors to the device. > > Signed-off-by: Sahil Siddiq <sahil...@proton.me> > --- > Changes from v4 -> v5: > - This was commit #2 in v4. This has been reordered to commit #3 > based on review comments. > - vhost-shadow-virtqueue.c: > (vhost_svq_valid_features): Move addition of enums to commit #6 > based on review comments. > (vhost_svq_add_packed): Set head_idx to buffer id instead of vring's > index. > (vhost_svq_kick): Split into vhost_svq_kick_split and > vhost_svq_kick_packed. > (vhost_svq_add): Use new vhost_svq_kick_* functions. > > hw/virtio/vhost-shadow-virtqueue.c | 117 +++++++++++++++++++++++++++-- > 1 file changed, 112 insertions(+), 5 deletions(-) > > diff --git a/hw/virtio/vhost-shadow-virtqueue.c > b/hw/virtio/vhost-shadow-virtqueue.c > index 4f74ad402a..6e16cd4bdf 100644 > --- a/hw/virtio/vhost-shadow-virtqueue.c > +++ b/hw/virtio/vhost-shadow-virtqueue.c > @@ -193,10 +193,83 @@ static void vhost_svq_add_split(VhostShadowVirtqueue > *svq, > /* Update the avail index after write the descriptor */ > smp_wmb(); > avail->idx = cpu_to_le16(svq->shadow_avail_idx); > +} > + > +/** > + * Write descriptors to SVQ packed vring > + * > + * @svq: The shadow virtqueue > + * @out_sg: The iovec to the guest > + * @out_num: Outgoing iovec length > + * @in_sg: The iovec from the guest > + * @in_num: Incoming iovec length > + * @sgs: Cache for hwaddr > + * @head: Saves current free_head > + */ > +static void vhost_svq_add_packed(VhostShadowVirtqueue *svq, > + const struct iovec *out_sg, size_t out_num, > + const struct iovec *in_sg, size_t in_num, > + hwaddr *sgs, unsigned *head) > +{ > + uint16_t id, curr, i, head_flags = 0, head_idx; > + size_t num = out_num + in_num; > + unsigned n; > + > + struct vring_packed_desc *descs = svq->vring_packed.vring.desc; > + > + head_idx = svq->vring_packed.next_avail_idx; > + i = head_idx; > + id = svq->free_head; > + curr = id; > + *head = id; > + > + /* Write descriptors to SVQ packed vring */ > + for (n = 0; n < num; n++) { > + uint16_t flags = cpu_to_le16(svq->vring_packed.avail_used_flags | > + (n < out_num ? 0 : VRING_DESC_F_WRITE) | > + (n + 1 == num ? 0 : VRING_DESC_F_NEXT)); > + if (i == head_idx) { > + head_flags = flags; > + } else { > + descs[i].flags = flags; > + } > + > + descs[i].addr = cpu_to_le64(sgs[n]); > + descs[i].id = id; > + if (n < out_num) { > + descs[i].len = cpu_to_le32(out_sg[n].iov_len); > + } else { > + descs[i].len = cpu_to_le32(in_sg[n - out_num].iov_len); > + } > + > + curr = cpu_to_le16(svq->desc_next[curr]); > + > + if (++i >= svq->vring_packed.vring.num) { > + i = 0; > + svq->vring_packed.avail_used_flags ^= > + 1 << VRING_PACKED_DESC_F_AVAIL | > + 1 << VRING_PACKED_DESC_F_USED; > + } > + } > > + if (i <= head_idx) { > + svq->vring_packed.avail_wrap_counter ^= 1; > + } > + > + svq->vring_packed.next_avail_idx = i; > + svq->shadow_avail_idx = i; > + svq->free_head = curr; > + > + /* > + * A driver MUST NOT make the first descriptor in the list > + * available before all subsequent descriptors comprising > + * the list are made available. > + */ > + smp_wmb(); > + svq->vring_packed.vring.desc[head_idx].flags = head_flags; > } > > -static void vhost_svq_kick(VhostShadowVirtqueue *svq) > +static void vhost_svq_kick_split(VhostShadowVirtqueue *svq) > { > bool needs_kick; > > @@ -209,7 +282,8 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq) > if (virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) { > uint16_t avail_event = le16_to_cpu( > *(uint16_t *)(&svq->vring.used->ring[svq->vring.num])); > - needs_kick = vring_need_event(avail_event, svq->shadow_avail_idx, > svq->shadow_avail_idx - 1); > + needs_kick = vring_need_event(avail_event, svq->shadow_avail_idx, > + svq->shadow_avail_idx - 1); > } else { > needs_kick = > !(svq->vring.used->flags & > cpu_to_le16(VRING_USED_F_NO_NOTIFY)); > @@ -222,6 +296,30 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq) > event_notifier_set(&svq->hdev_kick); > } > > +static void vhost_svq_kick_packed(VhostShadowVirtqueue *svq) > +{ > + bool needs_kick; > + > + /* > + * We need to expose the available array entries before checking > + * notification suppressions. > + */ > + smp_mb(); > + > + if (virtio_vdev_has_feature(svq->vdev, VIRTIO_RING_F_EVENT_IDX)) { > + return;
It's weird SVQ does not need to kick if _F_EVENT_IDX. This should have code checking the device ring flags etc. > + } else { > + needs_kick = (svq->vring_packed.vring.device->flags != > + cpu_to_le16(VRING_PACKED_EVENT_FLAG_DISABLE)); > + } > + > + if (!needs_kick) { > + return; > + } > + > + event_notifier_set(&svq->hdev_kick); > +} > + > /** > * Add an element to a SVQ. > * > @@ -258,13 +356,22 @@ int vhost_svq_add(VhostShadowVirtqueue *svq, const > struct iovec *out_sg, > return -EINVAL; > } > > - vhost_svq_add_split(svq, out_sg, out_num, in_sg, > - in_num, sgs, &qemu_head); > + if (svq->is_packed) { > + vhost_svq_add_packed(svq, out_sg, out_num, in_sg, > + in_num, sgs, &qemu_head); > + } else { > + vhost_svq_add_split(svq, out_sg, out_num, in_sg, > + in_num, sgs, &qemu_head); > + } > > svq->num_free -= ndescs; > svq->desc_state[qemu_head].elem = elem; > svq->desc_state[qemu_head].ndescs = ndescs; > - vhost_svq_kick(svq); > + if (svq->is_packed) { > + vhost_svq_kick_packed(svq); > + } else { > + vhost_svq_kick_split(svq); > + } > return 0; > } > > -- > 2.48.1 >