Re: [RFC PATCH 7/9] vhost: Add vhost_svq_inject

[Eugenio Perez Martin]

On Mon, Feb 14, 2022 at 8:28 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> This allows qemu to inject packets to the device without guest's notice.
>
> This will be use to inject net CVQ messages to restore status in the 
> destination
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  hw/virtio/vhost-shadow-virtqueue.h |   2 +
>  hw/virtio/vhost-shadow-virtqueue.c | 142 ++++++++++++++++++++++++-----
>  2 files changed, 123 insertions(+), 21 deletions(-)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
> b/hw/virtio/vhost-shadow-virtqueue.h
> index bf3b658889..767b0a82ba 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -38,6 +38,8 @@ bool vhost_svq_ack_guest_features(uint64_t dev_features,
>                                    uint64_t guest_features,
>                                    uint64_t *acked_features);
>
> +bool vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
> +                      size_t out_num, size_t in_num);
>  void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
>  void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int 
> call_fd);
>  const EventNotifier *vhost_svq_get_dev_kick_notifier(
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
> b/hw/virtio/vhost-shadow-virtqueue.c
> index 2ba3c2966a..26938b059c 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -16,9 +16,11 @@
>
>  #include "qemu/error-report.h"
>  #include "qemu/main-loop.h"
> +#include "qemu/iov.h"
>
>  typedef struct SVQElement {
>      VirtQueueElement elem;
> +    bool not_from_guest;
>  } SVQElement;
>
>  /* Shadow virtqueue to relay notifications */
> @@ -311,19 +313,53 @@ static bool vhost_svq_add_split(VhostShadowVirtqueue 
> *svq,
>      /* We need some descriptors here */
>      assert(elem->out_num || elem->in_num);
>
> -    ok = vhost_svq_translate_addr(svq, sgs, elem->out_sg, elem->out_num);
> -    if (unlikely(!ok)) {
> -        return false;
> +    if (elem->out_sg && svq_elem->not_from_guest) {
> +        DMAMap map = {
> +            .translated_addr = (hwaddr)svq_elem->elem.out_sg->iov_base,
> +            .size = ROUND_UP(elem->out_sg->iov_len, 4096) - 1,
> +            .perm = IOMMU_RO,
> +        };
> +        int r = vhost_iova_tree_map_alloc(svq->iova_tree, &map);
> +
> +        elem->out_addr[0] = map.iova;
> +        assert(elem->out_num == 1);
> +        assert(r == IOVA_OK);
> +
> +        r = svq->map_ops->map(map.iova, map.size, (void 
> *)map.translated_addr,
> +                              true, svq->map_ops_opaque);
> +        assert(r == 0);
> +        sgs[0] = (void *)map.iova;
> +    } else {
> +        ok = vhost_svq_translate_addr(svq, sgs, elem->out_sg, elem->out_num);
> +        if (unlikely(!ok)) {
> +            return false;
> +        }
>      }
>      vhost_vring_write_descs(svq, sgs, elem->out_sg, elem->out_num,
>                              elem->in_num > 0, false);
>
> +    if (elem->in_sg && svq_elem->not_from_guest) {
> +        DMAMap map = {
> +            .translated_addr = (hwaddr)svq_elem->elem.in_sg->iov_base,
> +            .size = ROUND_UP(elem->in_sg->iov_len, 4096) - 1,
> +            .perm = IOMMU_RW,
> +        };
> +        int r = vhost_iova_tree_map_alloc(svq->iova_tree, &map);
>
> -    ok = vhost_svq_translate_addr(svq, sgs, elem->in_sg, elem->in_num);
> -    if (unlikely(!ok)) {
> -        return false;
> -    }
> +        elem->in_addr[0] = map.iova;
> +        assert(elem->out_num == 1);
> +        assert(r == IOVA_OK);
>
> +        r = svq->map_ops->map(map.iova, map.size, (void 
> *)map.translated_addr,
> +                              false, svq->map_ops_opaque);
> +        assert(r == 0);
> +        sgs[0] = (void *)map.iova;
> +    } else {
> +        ok = vhost_svq_translate_addr(svq, sgs, elem->in_sg, elem->in_num);
> +        if (unlikely(!ok)) {
> +            return false;
> +        }
> +    }
>      vhost_vring_write_descs(svq, sgs, elem->in_sg, elem->in_num, false, 
> true);
>
>      /*
> @@ -364,6 +400,43 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq)
>      event_notifier_set(&svq->hdev_kick);
>  }
>
> +bool vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
> +                      size_t out_num, size_t in_num)
> +{
> +    size_t out_size = iov_size(iov, out_num);
> +    size_t out_buf_size = ROUND_UP(out_size, 4096);
> +    size_t in_size = iov_size(iov + out_num, in_num);
> +    size_t in_buf_size = ROUND_UP(in_size, 4096);
> +    SVQElement *svq_elem;
> +    uint16_t num_slots = (in_num ? 1 : 0) + (out_num ? 1 : 0);
> +
> +    if (unlikely(num_slots == 0 || svq->next_guest_avail_elem ||
> +        vhost_svq_available_slots(svq) < num_slots)) {
> +        return false;
> +    }
> +
> +    svq_elem = virtqueue_alloc_element(sizeof(SVQElement), 1, 1);
> +    if (out_num) {
> +        void *out = qemu_memalign(4096, out_buf_size);
> +        svq_elem->elem.out_sg[0].iov_base = out;
> +        svq_elem->elem.out_sg[0].iov_len = out_size;
> +        iov_to_buf(iov, out_num, 0, out, out_size);
> +        memset(out + out_size, 0, out_buf_size - out_size);
> +    }
> +    if (in_num) {
> +        void *in = qemu_memalign(4096, in_buf_size);
> +        svq_elem->elem.in_sg[0].iov_base = in;
> +        svq_elem->elem.in_sg[0].iov_len = in_size;
> +        memset(in, 0, in_buf_size);
> +    }
> +
> +    svq_elem->not_from_guest = true;
> +    vhost_svq_add(svq, svq_elem);
> +    vhost_svq_kick(svq);
> +
> +    return true;
> +}
> +
>  /**
>   * Forward available buffers.
>   *
> @@ -512,23 +585,50 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
>              }
>
>              elem = &svq_elem->elem;
> -            if (unlikely(i >= svq->vring.num)) {
> -                virtio_error(svq->vdev,
> -                         "More than %u used buffers obtained in a %u size 
> SVQ",
> -                         i, svq->vring.num);
> -                virtqueue_fill(vq, elem, elem->len, i);
> -                virtqueue_flush(vq, i);
> -                i = 0;
> -            }
> -            virtqueue_fill(vq, elem, elem->len, i++);
> -
>              if (svq->ops && svq->ops->used_elem_handler) {
>                  svq->ops->used_elem_handler(svq->vdev, elem);
>              }
> +
> +            if (svq_elem->not_from_guest) {
> +                const DMAMap out_map = {
> +                    .iova = elem->out_addr[0],
> +                    .translated_addr = (hwaddr)elem->out_sg[0].iov_base,
> +                    .size = elem->out_sg[0].iov_len,
> +                };
> +                const DMAMap in_map = {
> +                    .iova = elem->in_addr[0],
> +                    .translated_addr = (hwaddr)elem->in_sg[0].iov_base,
> +                    .size = elem->in_sg[0].iov_len,
> +                };
> +                vhost_iova_tree_remove(svq->iova_tree, &out_map);
> +                if (svq->map_ops->unmap) {

This is actually bad, as is removing the SVQ element size, not the map size.

Same for the "in_map". I will fix it for the next revision.

Thanks!

> +                    svq->map_ops->unmap(out_map.iova, in_map.size,
> +                                        svq->map_ops_opaque);
> +                }
> +                qemu_vfree(elem->out_sg[0].iov_base);
> +                vhost_iova_tree_remove(svq->iova_tree, &in_map);
> +                if (svq->map_ops->unmap) {
> +                    svq->map_ops->unmap(out_map.iova, out_map.size,
> +                                        svq->map_ops_opaque);
> +                }
> +                qemu_vfree(elem->in_sg[0].iov_base);
> +            } else {
> +                if (unlikely(i >= svq->vring.num)) {
> +                    virtio_error(svq->vdev,
> +                        "More than %u used buffers obtained in a %u size 
> SVQ",
> +                        i, svq->vring.num);
> +                    virtqueue_fill(vq, elem, elem->len, i);
> +                    virtqueue_flush(vq, i);
> +                    i = 0;
> +                }
> +                virtqueue_fill(vq, elem, elem->len, i++);
> +            }
>          }
>
> -        virtqueue_flush(vq, i);
> -        event_notifier_set(&svq->svq_call);
> +        if (i > 0) {
> +            virtqueue_flush(vq, i);
> +            event_notifier_set(&svq->svq_call);
> +        }
>
>          if (check_for_avail_queue && svq->next_guest_avail_elem) {
>              /*
> @@ -704,14 +804,14 @@ void vhost_svq_stop(VhostShadowVirtqueue *svq)
>      for (unsigned i = 0; i < svq->vring.num; ++i) {
>          g_autofree SVQElement *svq_elem = NULL;
>          svq_elem = g_steal_pointer(&svq->ring_id_maps[i]);
> -        if (svq_elem)  {
> +        if (svq_elem && !svq_elem->not_from_guest)  {
>              virtqueue_detach_element(svq->vq, &svq_elem->elem,
>                                       svq_elem->elem.len);
>          }
>      }
>
>      next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
> -    if (next_avail_elem) {
> +    if (next_avail_elem && !next_avail_elem->not_from_guest) {
>          virtqueue_detach_element(svq->vq, &next_avail_elem->elem,
>                                   next_avail_elem->elem.len);
>      }
> --
> 2.27.0
>
>