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

[Jason Wang <jasowang@redhat.com>]

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()

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;