Re: [PATCH v4 01/15] vdpa net: move iova tree creation from init to start

[Jason Wang <jasowang@redhat.com>]

On Fri, Mar 3, 2023 at 4:01 PM Eugenio Perez Martin <eperezma@redhat.com> wrote:
>
> On Fri, Mar 3, 2023 at 4:32 AM Jason Wang <jasowang@redhat.com> wrote:
> >
> >
> > 在 2023/3/1 15:01, Eugenio Perez Martin 写道:
> > > On Mon, Feb 27, 2023 at 8:04 AM Jason Wang <jasowang@redhat.com> wrote:
> > >>
> > >> 在 2023/2/24 23:54, Eugenio Pérez 写道:
> > >>> Only create iova_tree if and when it is needed.
> > >>>
> > >>> The cleanup keeps being responsible of last VQ but this change allows it
> > >>> to merge both cleanup functions.
> > >>>
> > >>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > >>> Acked-by: Jason Wang <jasowang@redhat.com>
> > >>> ---
> > >>> v4:
> > >>> * Remove leak of iova_tree because double allocation
> > >>> * Document better the sharing of IOVA tree between data and CVQ
> > >>> ---
> > >>>    net/vhost-vdpa.c | 113 ++++++++++++++++++++++++++++++++++-------------
> > >>>    1 file changed, 83 insertions(+), 30 deletions(-)
> > >>>
> > >>> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> > >>> index de5ed8ff22..b89c99066a 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;
> > >>> +    }
> > >>> +
> > >>> +    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,
> > >>
> > >> Looking at the implementation, it seems nothing net specific, any reason
> > >> we can't simply use vhost_vdpa_dev_start()?
> > >>
> > > IOVA tree must be shared between (at least) all dataplane vhost_vdpa.
> > > How could we move the call to vhost_vdpa_net_first_nc_vdpa to
> > > vhost_vdpa_dev_start?
> >
> >
> > Ok, I think I get it. We should really consider to implement a parent
> > structure in the future for vhost_vdpa then we can avoid tricks like:
> >
> > vq_index_end and vhost_vdpa_net_first_nc_vdpa()
> >
>
> Sounds right. Maybe it is enough to link all of them with a QLIST?

That's also fine but you need to place the parent data into the head
structure which seems not clean than having pointers to point to the
same parent structure.

Thanks

>
> Thanks!
>
> > Thanks
> >
> >
> > >
> > > A possibility is to always allocate it just in case. But it seems to
> > > me it is better to not start allocating resources just in case :).
> > >
> > >>>            .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 +473,27 @@ out:
> > >>>            return 0;
> > >>>        }
> > >>>
> > >>> +    s0 = vhost_vdpa_net_first_nc_vdpa(s);
> > >>> +    if (s0->vhost_vdpa.iova_tree) {
> > >>> +        /*
> > >>> +         * SVQ is already configured for all virtqueues.  Reuse IOVA tree for
> > >>> +         * simplicity, wether CVQ shares ASID with guest or not, because:
> > >>
> > >> Typo, should be "whether", or "regardless of whether"(not a native speaker).
> > >>
> > > Good catch, I can fix it in the next version.
> > >
> > > Thanks!
> > >
> > >> Other looks good.
> > >>
> > >> Thanks
> > >>
> > >>
> > >>> +         * - Memory listener need access to guest's memory addresses allocated
> > >>> +         *   in the IOVA tree.
> > >>> +         * - There should be plenty of IOVA address space for both ASID not to
> > >>> +         *   worry about collisions between them.  Guest's translations are
> > >>> +         *   still validated with virtio virtqueue_pop so there is no risk for
> > >>> +         *   the guest to access memory it shouldn't.
> > >>> +         *
> > >>> +         * To allocate a iova tree per ASID is doable but it complicates the
> > >>> +         * code and it is not worth for the moment.
> > >>> +         */
> > >>> +        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 +518,9 @@ 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 +730,7 @@ 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 +752,6 @@ 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 +821,6 @@ 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 +872,8 @@ 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 +881,7 @@ 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 +889,11 @@ 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 +903,6 @@ err:
> > >>>            }
> > >>>        }
> > >>>
> > >>> -err_svq:
> > >>>        qemu_close(vdpa_device_fd);
> > >>>
> > >>>        return -1;
> >
>