Re: [PATCH v2 01/13] vdpa net: move iova tree creation from init to start

[Si-Wei Liu <si-wei.liu@oracle.com>]

On 2/13/2023 3:14 AM, Eugenio Perez Martin wrote:
> On Mon, Feb 13, 2023 at 7:51 AM Si-Wei Liu <si-wei.liu@oracle.com> wrote:
>>
>>
>> On 2/8/2023 1:42 AM, Eugenio Pérez wrote:
>>> 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>
>>> ---
>>>    net/vhost-vdpa.c | 99 ++++++++++++++++++++++++++++++++++--------------
>>>    1 file changed, 71 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
>>> index de5ed8ff22..a9e6c8f28e 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,
>>>            .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;
>>> @@ -425,6 +475,15 @@ 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);
>> I wonder how this case could happen, vhost_vdpa_net_data_start_first()
>> should've allocated an iova tree on the first data vq. Is zero data vq
>> ever possible on net vhost-vdpa?
>>
> It's the case of the current qemu master when only CVQ is being
> shadowed. It's not that "there are no data vq": If that case were
> possible, CVQ vhost-vdpa state would be s0.
>
> The case is that since only CVQ vhost-vdpa is the one being migrated,
> only CVQ has an iova tree.
OK, so this corresponds to the case where live migration is not started 
and CVQ starts in its own address space of VHOST_VDPA_NET_CVQ_ASID. 
Thanks for explaining it!

>
> With this series applied and with no migration running, the case is
> the same as before: only SVQ gets shadowed. When migration starts, all
> vqs are migrated, and share iova tree.
I wonder what is the reason to share the iova tree when migration 
starts, I think CVQ may stay on its own VHOST_VDPA_NET_CVQ_ASID still?

Actually there's discrepancy in vhost_vdpa_net_log_global_enable(), I 
don't see explicit code to switch from VHOST_VDPA_NET_CVQ_ASID to 
VHOST_VDPA_GUEST_PA_ASID for the CVQ. This is the address space I 
collision I mentioned earlier:

9585@1676093788.259201:vhost_vdpa_dma_map vdpa:0x7ff13088a190 fd: 16 
msg_type: 2 asid: 0 iova: 0x1000 size: 0x2000 uaddr: 0x55a5a7ff3000 
perm: 0x1 type: 2
9585@1676093788.279923:vhost_vdpa_dma_map vdpa:0x7ff13088a190 fd: 16 
msg_type: 2 asid: 0 iova: 0x3000 size: 0x1000 uaddr: 0x55a5a7ff6000 
perm: 0x3 type: 2
9585@1676093788.290529:vhost_vdpa_set_vring_addr dev: 0x55a5a77cec20 
index: 0 flags: 0x0 desc_user_addr: 0x1000 used_user_addr: 0x3000 
avail_user_addr: 0x2000 log_guest_addr: 0x0
:
:
9585@1676093788.543567:vhost_vdpa_dma_map vdpa:0x7ff1302b6190 fd: 16 
msg_type: 2 asid: 0 iova: 0x16000 size: 0x2000 uaddr: 0x55a5a7959000 
perm: 0x1 type: 2
9585@1676093788.576923:vhost_vdpa_dma_map vdpa:0x7ff1302b6190 fd: 16 
msg_type: 2 asid: 0 iova: 0x18000 size: 0x1000 uaddr: 0x55a5a795c000 
perm: 0x3 type: 2
9585@1676093788.593881:vhost_vdpa_set_vring_addr dev: 0x55a5a7580930 
index: 7 flags: 0x0 desc_user_addr: 0x16000 used_user_addr: 0x18000 
avail_user_addr: 0x17000 log_guest_addr: 0x0
9585@1676093788.593904:vhost_vdpa_dma_map vdpa:0x7ff13026d190 fd: 16 
msg_type: 2 asid: 1 iova: 0x19000 size: 0x1000 uaddr: 0x55a5a77f8000 
perm: 0x1 type: 2
9585@1676093788.606448:vhost_vdpa_dma_map vdpa:0x7ff13026d190 fd: 16 
msg_type: 2 asid: 1 iova: 0x1a000 size: 0x1000 uaddr: 0x55a5a77fa000 
perm: 0x3 type: 2
9585@1676093788.616253:vhost_vdpa_dma_map vdpa:0x7ff13026d190 fd: 16 
msg_type: 2 asid: 1 iova: 0x1b000 size: 0x1000 uaddr: 0x55a5a795f000 
perm: 0x1 type: 2
9585@1676093788.625956:vhost_vdpa_dma_map vdpa:0x7ff13026d190 fd: 16 
msg_type: 2 asid: 1 iova: 0x1c000 size: 0x1000 uaddr: 0x55a5a7f4e000 
perm: 0x3 type: 2
9585@1676093788.635655:vhost_vdpa_set_vring_addr dev: 0x55a5a7580ec0 
index: 8 flags: 0x0 desc_user_addr: 0x1b000 used_user_addr: 0x1c000 
avail_user_addr: 0x1b400 log_guest_addr: 0x0
9585@1676093788.635667:vhost_vdpa_listener_region_add vdpa: 
0x7ff13026d190 iova 0x0 llend 0xa0000 vaddr: 0x7fef1fe00000 read-only: 0
9585@1676093788.635670:vhost_vdpa_listener_begin_batch 
vdpa:0x7ff13026d190 fd: 16 msg_type: 2 type: 5
9585@1676093788.635677:vhost_vdpa_dma_map vdpa:0x7ff13026d190 fd: 16 
msg_type: 2 asid: 0 iova: 0x0 size: 0xa0000 uaddr: 0x7fef1fe00000 perm: 
0x3 type: 2
2023-02-11T05:36:28.635686Z qemu-system-x86_64: failed to write, fd=16, 
errno=14 (Bad address)
2023-02-11T05:36:28.635721Z qemu-system-x86_64: vhost vdpa map fail!
2023-02-11T05:36:28.635744Z qemu-system-x86_64: vhost-vdpa: DMA mapping 
failed, unable to continue


Regards,
-Siwei
>
> Thanks!
>
>> Thanks,
>> -Siwei
>>> +    }
>>> +
>>>        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 +508,9 @@ 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 +720,7 @@ 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 +742,6 @@ 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 +811,6 @@ 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 +862,8 @@ 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 +871,7 @@ 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 +879,11 @@ 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 +893,6 @@ err:
>>>            }
>>>        }
>>>
>>> -err_svq:
>>>        qemu_close(vdpa_device_fd);
>>>
>>>        return -1;