Re: [Qemu-devel] [PATCH RFC v6 07/20] virtio: allow virtio-1 queue layout

[David Gibson]

On Thu, Dec 11, 2014 at 02:25:09PM +0100, Cornelia Huck wrote:
> For virtio-1 devices, we allow a more complex queue layout that doesn't
> require descriptor table and rings on a physically-contigous memory area:
> add virtio_queue_set_rings() to allow transports to set this up.
> 
> Signed-off-by: Cornelia Huck <address@hidden>
> ---
>  hw/virtio/virtio-mmio.c    |    3 +++
>  hw/virtio/virtio.c         |   53 
> ++++++++++++++++++++++++++++----------------
>  include/hw/virtio/virtio.h |    3 +++
>  3 files changed, 40 insertions(+), 19 deletions(-)
> 
> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
> index 43b7e02..0c9b63b 100644
> --- a/hw/virtio/virtio-mmio.c
> +++ b/hw/virtio/virtio-mmio.c
> @@ -244,8 +244,11 @@ static void virtio_mmio_write(void *opaque, hwaddr 
> offset, uint64_t value,
>      case VIRTIO_MMIO_QUEUENUM:
>          DPRINTF("mmio_queue write %d max %d\n", (int)value, 
> VIRTQUEUE_MAX_SIZE);
>          virtio_queue_set_num(vdev, vdev->queue_sel, value);
> +        /* Note: only call this function for legacy devices */

It's not clear to me if this is an assertion that this *does* only
call the function for legacy devices or a fixme, that it *should* only
call the function for legacy devices.

> +        virtio_queue_update_rings(vdev, vdev->queue_sel);
>          break;
>      case VIRTIO_MMIO_QUEUEALIGN:
> +        /* Note: this is only valid for legacy devices */
>          virtio_queue_set_align(vdev, vdev->queue_sel, value);
>          break;
>      case VIRTIO_MMIO_QUEUEPFN:
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 8f69ffa..57190ba 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -69,7 +69,6 @@ typedef struct VRing
>  struct VirtQueue
>  {
>      VRing vring;
> -    hwaddr pa;
>      uint16_t last_avail_idx;
>      /* Last used index value we have signalled on */
>      uint16_t signalled_used;
> @@ -92,15 +91,18 @@ struct VirtQueue
>  };
>  
>  /* virt queue functions */
> -static void virtqueue_init(VirtQueue *vq)
> +void virtio_queue_update_rings(VirtIODevice *vdev, int n)

Perhaps something in the name to emphasise that this is only for <v1.0
devices?

>  {
> -    hwaddr pa = vq->pa;
> +    VRing *vring = &vdev->vq[n].vring;
>  
> -    vq->vring.desc = pa;
> -    vq->vring.avail = pa + vq->vring.num * sizeof(VRingDesc);
> -    vq->vring.used = vring_align(vq->vring.avail +
> -                                 offsetof(VRingAvail, ring[vq->vring.num]),
> -                                 vq->vring.align);
> +    if (!vring->desc) {
> +        /* not yet setup -> nothing to do */
> +        return;
> +    }
> +    vring->avail = vring->desc + vring->num * sizeof(VRingDesc);
> +    vring->used = vring_align(vring->avail +
> +                              offsetof(VRingAvail, ring[vring->num]),
> +                              vring->align);

Would it make sense to implement this in terms of
virtio_queue_set_rings()?

>  }
>  
>  static inline uint64_t vring_desc_addr(VirtIODevice *vdev, hwaddr desc_pa,
> @@ -605,7 +607,6 @@ void virtio_reset(void *opaque)
>          vdev->vq[i].vring.avail = 0;
>          vdev->vq[i].vring.used = 0;
>          vdev->vq[i].last_avail_idx = 0;
> -        vdev->vq[i].pa = 0;
>          vdev->vq[i].vector = VIRTIO_NO_VECTOR;
>          vdev->vq[i].signalled_used = 0;
>          vdev->vq[i].signalled_used_valid = false;
> @@ -708,13 +709,21 @@ void virtio_config_writel(VirtIODevice *vdev, uint32_t 
> addr, uint32_t data)
>  
>  void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)
>  {
> -    vdev->vq[n].pa = addr;
> -    virtqueue_init(&vdev->vq[n]);
> +    vdev->vq[n].vring.desc = addr;
> +    virtio_queue_update_rings(vdev, n);
>  }
>  
>  hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
>  {
> -    return vdev->vq[n].pa;
> +    return vdev->vq[n].vring.desc;
> +}
> +
> +void virtio_queue_set_rings(VirtIODevice *vdev, int n, hwaddr desc,
> +                            hwaddr avail, hwaddr used)
> +{
> +    vdev->vq[n].vring.desc = desc;
> +    vdev->vq[n].vring.avail = avail;
> +    vdev->vq[n].vring.used = used;
>  }
>  
>  void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
> @@ -728,7 +737,6 @@ void virtio_queue_set_num(VirtIODevice *vdev, int n, int 
> num)
>          return;
>      }
>      vdev->vq[n].vring.num = num;
> -    virtqueue_init(&vdev->vq[n]);
>  }
>  
>  int virtio_queue_get_num(VirtIODevice *vdev, int n)
> @@ -748,6 +756,11 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, 
> int align)
>      BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
>      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
>  
> +    /* virtio-1 compliant devices cannot change the aligment */
> +    if (virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> +        error_report("tried to modify queue alignment for virtio-1 device");
> +        return;
> +    }
>      /* Check that the transport told us it was going to do this
>       * (so a buggy transport will immediately assert rather than
>       * silently failing to migrate this state)
> @@ -755,7 +768,7 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, 
> int align)
>      assert(k->has_variable_vring_alignment);
>  
>      vdev->vq[n].vring.align = align;
> -    virtqueue_init(&vdev->vq[n]);
> +    virtio_queue_update_rings(vdev, n);
>  }
>  
>  void virtio_queue_notify_vq(VirtQueue *vq)
> @@ -949,7 +962,8 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
>          if (k->has_variable_vring_alignment) {
>              qemu_put_be32(f, vdev->vq[i].vring.align);
>          }
> -        qemu_put_be64(f, vdev->vq[i].pa);
> +        /* XXX virtio-1 devices */
> +        qemu_put_be64(f, vdev->vq[i].vring.desc);
>          qemu_put_be16s(f, &vdev->vq[i].last_avail_idx);
>          if (k->save_queue) {
>              k->save_queue(qbus->parent, i, f);
> @@ -1044,13 +1058,14 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int 
> version_id)
>          if (k->has_variable_vring_alignment) {
>              vdev->vq[i].vring.align = qemu_get_be32(f);
>          }
> -        vdev->vq[i].pa = qemu_get_be64(f);
> +        vdev->vq[i].vring.desc = qemu_get_be64(f);
>          qemu_get_be16s(f, &vdev->vq[i].last_avail_idx);
>          vdev->vq[i].signalled_used_valid = false;
>          vdev->vq[i].notification = true;
>  
> -        if (vdev->vq[i].pa) {
> -            virtqueue_init(&vdev->vq[i]);
> +        if (vdev->vq[i].vring.desc) {
> +            /* XXX virtio-1 devices */
> +            virtio_queue_update_rings(vdev, i);
>          } else if (vdev->vq[i].last_avail_idx) {
>              error_report("VQ %d address 0x0 "
>                           "inconsistent with Host index 0x%x",
> @@ -1084,7 +1099,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int 
> version_id)
>      }
>  
>      for (i = 0; i < num; i++) {
> -        if (vdev->vq[i].pa) {
> +        if (vdev->vq[i].vring.desc) {
>              uint16_t nheads;
>              nheads = vring_avail_idx(&vdev->vq[i]) - 
> vdev->vq[i].last_avail_idx;
>              /* Check it isn't doing strange things with descriptor numbers. 
> */
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 68c40db..b63ced3 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -224,6 +224,9 @@ void virtio_queue_set_addr(VirtIODevice *vdev, int n, 
> hwaddr addr);
>  hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n);
>  void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
>  int virtio_queue_get_num(VirtIODevice *vdev, int n);
> +void virtio_queue_set_rings(VirtIODevice *vdev, int n, hwaddr desc,
> +                            hwaddr avail, hwaddr used);
> +void virtio_queue_update_rings(VirtIODevice *vdev, int n);
>  void virtio_queue_set_align(VirtIODevice *vdev, int n, int align);
>  void virtio_queue_notify(VirtIODevice *vdev, int n);
>  uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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