Re: [RFC v2 02/13] vdpa net: move iova tree creation from init to start

[Jason Wang <jasowang@redhat.com>]

在 2023/1/13 15:28, Eugenio Perez Martin 写道:
> On Fri, Jan 13, 2023 at 4:53 AM Jason Wang <jasowang@redhat.com> wrote:
>> On Fri, Jan 13, 2023 at 1:24 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>>> Only create iova_tree if and when it is needed.
>>>
>>> The cleanup keeps being responsability of last VQ but this change allows
>>> to merge both cleanup functions.
>>>
>>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
>>> ---
>>>   net/vhost-vdpa.c | 101 +++++++++++++++++++++++++++++++++--------------
>>>   1 file changed, 71 insertions(+), 30 deletions(-)
>>>
>>> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
>>> index de5ed8ff22..75cca497c8 100644
>>> --- a/net/vhost-vdpa.c
>>> +++ b/net/vhost-vdpa.c
>>> @@ -178,13 +178,9 @@ err_init:
>>>   static void vhost_vdpa_cleanup(NetClientState *nc)
>>>   {
>>>       VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
>>> -    struct vhost_dev *dev = &s->vhost_net->dev;
>>>
>>>       qemu_vfree(s->cvq_cmd_out_buffer);
>>>       qemu_vfree(s->status);
>>> -    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
>>> -        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
>>> -    }
>>>       if (s->vhost_net) {
>>>           vhost_net_cleanup(s->vhost_net);
>>>           g_free(s->vhost_net);
>>> @@ -234,10 +230,64 @@ static ssize_t vhost_vdpa_receive(NetClientState *nc, const uint8_t *buf,
>>>       return size;
>>>   }
>>>
>>> +/** From any vdpa net client, get the netclient of first queue pair */
>>> +static VhostVDPAState *vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
>>> +{
>>> +    NICState *nic = qemu_get_nic(s->nc.peer);
>>> +    NetClientState *nc0 = qemu_get_peer(nic->ncs, 0);
>>> +
>>> +    return DO_UPCAST(VhostVDPAState, nc, nc0);
>>> +}
>>> +
>>> +static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
>>> +{
>>> +    struct vhost_vdpa *v = &s->vhost_vdpa;
>>> +
>>> +    if (v->shadow_vqs_enabled) {
>>> +        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
>>> +                                           v->iova_range.last);
>>> +    }
>>> +}
>>> +
>>> +static int vhost_vdpa_net_data_start(NetClientState *nc)
>>> +{
>>> +    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
>>> +    struct vhost_vdpa *v = &s->vhost_vdpa;
>>> +
>>> +    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>>> +
>>> +    if (v->index == 0) {
>>> +        vhost_vdpa_net_data_start_first(s);
>>> +        return 0;
>>> +    }
>>> +
>>> +    if (v->shadow_vqs_enabled) {
>>> +        VhostVDPAState *s0 = vhost_vdpa_net_first_nc_vdpa(s);
>>> +        v->iova_tree = s0->vhost_vdpa.iova_tree;
>>> +    }
>> It looks to me the logic here is somehow the same as
>> vhost_vdpa_net_cvq_start(), can we unify the them?
>>
> It depends on what you mean by unify :). But we can explore it for sure.
>
> We can call vhost_vdpa_net_data_start, but the steps to do if
> s0->vhost_vdpa.iova_tree == NULL are different. Data queues must do
> nothing, but CVQ must create a new iova tree.
>
> So one possibility is to convert this part of vhost_vdpa_net_cvq_start:
>      s0 = vhost_vdpa_net_first_nc_vdpa(s);
>      if (s0->vhost_vdpa.iova_tree) {
>          /* SVQ is already configured for all virtqueues */
>          v->iova_tree = s0->vhost_vdpa.iova_tree;
>      } else {
>          v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
>                                             v->iova_range.last);
>      }
>
> into:
>      vhost_vdpa_net_data_start(nc);
>      if (!v->iova_tree) {
>          v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
>                                             v->iova_range.last);
>      }
>
> I'm ok with the change but it's less clear in my opinion: it's not
> obvious that net_data_start is in charge of setting v->iova_tree to
> me.


Ok.


>
> Another possibility is to abstract something like
> first_nc_iova_tree(), but we need to check more fields of s0 later
> (shadow_data) so I'm not sure about the benefit.
>
> Is that what you have in mind?


Kind of, but I think we can leave the code as is.

In the future, as discussed, we need to introduce something like a 
parent or opaque structure for NetClientState structure, it can simply a 
lot of things: we can have one same common parent for all queues, then 
there's no need for the trick like first_nc_iova_tree() and other 
similar tricks.

Thanks

>
> Thanks!
>
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static void vhost_vdpa_net_client_stop(NetClientState *nc)
>>> +{
>>> +    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
>>> +    struct vhost_dev *dev;
>>> +
>>> +    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>>> +
>>> +    dev = s->vhost_vdpa.dev;
>>> +    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
>>> +        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
>>> +    }
>>> +}
>>> +
>>>   static NetClientInfo net_vhost_vdpa_info = {
>>>           .type = NET_CLIENT_DRIVER_VHOST_VDPA,
>>>           .size = sizeof(VhostVDPAState),
>>>           .receive = vhost_vdpa_receive,
>>> +        .start = vhost_vdpa_net_data_start,
>>> +        .stop = vhost_vdpa_net_client_stop,
>>>           .cleanup = vhost_vdpa_cleanup,
>>>           .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
>>>           .has_ufo = vhost_vdpa_has_ufo,
>>> @@ -351,7 +401,7 @@ dma_map_err:
>>>
>>>   static int vhost_vdpa_net_cvq_start(NetClientState *nc)
>>>   {
>>> -    VhostVDPAState *s;
>>> +    VhostVDPAState *s, *s0;
>>>       struct vhost_vdpa *v;
>>>       uint64_t backend_features;
>>>       int64_t cvq_group;
>>> @@ -415,8 +465,6 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
>>>           return r;
>>>       }
>>>
>>> -    v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
>>> -                                       v->iova_range.last);
>>>       v->shadow_vqs_enabled = true;
>>>       s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_ASID;
>>>
>>> @@ -425,6 +473,15 @@ out:
>>>           return 0;
>>>       }
>>>
>>> +    s0 = vhost_vdpa_net_first_nc_vdpa(s);
>>> +    if (s0->vhost_vdpa.iova_tree) {
>>> +        /* SVQ is already configured for all virtqueues */
>>> +        v->iova_tree = s0->vhost_vdpa.iova_tree;
>>> +    } else {
>>> +        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
>>> +                                           v->iova_range.last);
>>> +    }
>>> +
>>>       r = vhost_vdpa_cvq_map_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer,
>>>                                  vhost_vdpa_net_cvq_cmd_page_len(), false);
>>>       if (unlikely(r < 0)) {
>>> @@ -449,15 +506,9 @@ static void vhost_vdpa_net_cvq_stop(NetClientState *nc)
>>>       if (s->vhost_vdpa.shadow_vqs_enabled) {
>>>           vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
>>>           vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
>>> -        if (!s->always_svq) {
>>> -            /*
>>> -             * If only the CVQ is shadowed we can delete this safely.
>>> -             * If all the VQs are shadows this will be needed by the time the
>>> -             * device is started again to register SVQ vrings and similar.
>>> -             */
>>> -            g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
>>> -        }
>>>       }
>>> +
>>> +    vhost_vdpa_net_client_stop(nc);
>>>   }
>>>
>>>   static ssize_t vhost_vdpa_net_cvq_add(VhostVDPAState *s, size_t out_len,
>>> @@ -667,8 +718,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
>>>                                          int nvqs,
>>>                                          bool is_datapath,
>>>                                          bool svq,
>>> -                                       struct vhost_vdpa_iova_range iova_range,
>>> -                                       VhostIOVATree *iova_tree)
>>> +                                       struct vhost_vdpa_iova_range iova_range)
>>>   {
>>>       NetClientState *nc = NULL;
>>>       VhostVDPAState *s;
>>> @@ -690,7 +740,6 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
>>>       s->vhost_vdpa.shadow_vqs_enabled = svq;
>>>       s->vhost_vdpa.iova_range = iova_range;
>>>       s->vhost_vdpa.shadow_data = svq;
>>> -    s->vhost_vdpa.iova_tree = iova_tree;
>>>       if (!is_datapath) {
>>>           s->cvq_cmd_out_buffer = qemu_memalign(qemu_real_host_page_size(),
>>>                                               vhost_vdpa_net_cvq_cmd_page_len());
>>> @@ -760,7 +809,6 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
>>>       uint64_t features;
>>>       int vdpa_device_fd;
>>>       g_autofree NetClientState **ncs = NULL;
>>> -    g_autoptr(VhostIOVATree) iova_tree = NULL;
>>>       struct vhost_vdpa_iova_range iova_range;
>>>       NetClientState *nc;
>>>       int queue_pairs, r, i = 0, has_cvq = 0;
>>> @@ -812,12 +860,8 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
>>>           goto err;
>>>       }
>>>
>>> -    if (opts->x_svq) {
>>> -        if (!vhost_vdpa_net_valid_svq_features(features, errp)) {
>>> -            goto err_svq;
>>> -        }
>>> -
>>> -        iova_tree = vhost_iova_tree_new(iova_range.first, iova_range.last);
>>> +    if (opts->x_svq && !vhost_vdpa_net_valid_svq_features(features, errp)) {
>>> +        goto err;
>>>       }
>>>
>>>       ncs = g_malloc0(sizeof(*ncs) * queue_pairs);
>>> @@ -825,7 +869,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
>>>       for (i = 0; i < queue_pairs; i++) {
>>>           ncs[i] = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
>>>                                        vdpa_device_fd, i, 2, true, opts->x_svq,
>>> -                                     iova_range, iova_tree);
>>> +                                     iova_range);
>>>           if (!ncs[i])
>>>               goto err;
>>>       }
>>> @@ -833,13 +877,11 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
>>>       if (has_cvq) {
>>>           nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
>>>                                    vdpa_device_fd, i, 1, false,
>>> -                                 opts->x_svq, iova_range, iova_tree);
>>> +                                 opts->x_svq, iova_range);
>>>           if (!nc)
>>>               goto err;
>>>       }
>>>
>>> -    /* iova_tree ownership belongs to last NetClientState */
>>> -    g_steal_pointer(&iova_tree);
>>>       return 0;
>>>
>>>   err:
>>> @@ -849,7 +891,6 @@ err:
>>>           }
>>>       }
>>>
>>> -err_svq:
>>>       qemu_close(vdpa_device_fd);
>>>
>>>       return -1;
>>> --
>>> 2.31.1
>>>