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From:   Chia-I Wu <olvaffe@gmail.com>
Date:   Sun, 30 Jun 2019 11:29:45 -0700
Message-ID: <CAPaKu7Qab2XyWs830YHK8iAcVUXX3KPt_5CT_U9MmivGc3iJ4Q@mail.gmail.com>
Subject: Re: [PATCH v5 08/12] drm/virtio: rework virtio_gpu_execbuffer_ioctl fencing
To:     Gerd Hoffmann <kraxel@redhat.com>
Cc:     ML dri-devel <dri-devel@lists.freedesktop.org>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@lists.linux-foundation.org>,
        open list <linux-kernel@vger.kernel.org>
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On Sun, Jun 30, 2019 at 11:20 AM Chia-I Wu <olvaffe@gmail.com> wrote:
>
> On Fri, Jun 28, 2019 at 5:13 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
> >
> > Use gem reservation helpers and direct reservation_object_* calls
> > instead of ttm.
> >
> > v5: fix fencing (Chia-I Wu).
> > v3: Also attach the array of gem objects to the virtio command buffer,
> > so we can drop the object references in the completion callback.  Needed
> > because ttm fence helpers grab a reference for us, but gem helpers
> > don't.
> There are other places
There are other places where a vbuffer uses objects, such as in
transfers.  Do we need to make sure the objects are alive in those
places?

> >
> > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> > Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > ---
> >  drivers/gpu/drm/virtio/virtgpu_drv.h   |  6 ++-
> >  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 62 +++++++++++---------------
> >  drivers/gpu/drm/virtio/virtgpu_vq.c    | 17 ++++---
> >  3 files changed, 43 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> > index 98d646789d23..356d27132388 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> > @@ -120,9 +120,9 @@ struct virtio_gpu_vbuffer {
> >
> >         char *resp_buf;
> >         int resp_size;
> > -
> >         virtio_gpu_resp_cb resp_cb;
> >
> > +       struct virtio_gpu_object_array *objs;
> >         struct list_head list;
> >  };
> >
> > @@ -311,7 +311,9 @@ void virtio_gpu_cmd_context_detach_resource(struct virtio_gpu_device *vgdev,
> >                                             uint32_t resource_id);
> >  void virtio_gpu_cmd_submit(struct virtio_gpu_device *vgdev,
> >                            void *data, uint32_t data_size,
> > -                          uint32_t ctx_id, struct virtio_gpu_fence *fence);
> > +                          uint32_t ctx_id,
> > +                          struct virtio_gpu_object_array *objs,
> > +                          struct virtio_gpu_fence *fence);
> >  void virtio_gpu_cmd_transfer_from_host_3d(struct virtio_gpu_device *vgdev,
> >                                           uint32_t resource_id, uint32_t ctx_id,
> >                                           uint64_t offset, uint32_t level,
> > diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> > index 0caff3fa623e..ae6830aa38c9 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> > @@ -105,14 +105,11 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> >         struct drm_virtgpu_execbuffer *exbuf = data;
> >         struct virtio_gpu_device *vgdev = dev->dev_private;
> >         struct virtio_gpu_fpriv *vfpriv = drm_file->driver_priv;
> > -       struct drm_gem_object *gobj;
> >         struct virtio_gpu_fence *out_fence;
> > -       struct virtio_gpu_object *qobj;
> >         int ret;
> >         uint32_t *bo_handles = NULL;
> >         void __user *user_bo_handles = NULL;
> > -       struct list_head validate_list;
> > -       struct ttm_validate_buffer *buflist = NULL;
> > +       struct virtio_gpu_object_array *buflist = NULL;
> >         int i;
> >         struct ww_acquire_ctx ticket;
> >         struct sync_file *sync_file;
> > @@ -155,15 +152,10 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> >                         return out_fence_fd;
> >         }
> >
> > -       INIT_LIST_HEAD(&validate_list);
> >         if (exbuf->num_bo_handles) {
> > -
> >                 bo_handles = kvmalloc_array(exbuf->num_bo_handles,
> > -                                          sizeof(uint32_t), GFP_KERNEL);
> > -               buflist = kvmalloc_array(exbuf->num_bo_handles,
> > -                                          sizeof(struct ttm_validate_buffer),
> > -                                          GFP_KERNEL | __GFP_ZERO);
> > -               if (!bo_handles || !buflist) {
> > +                                           sizeof(uint32_t), GFP_KERNEL);
> > +               if (!bo_handles) {
> >                         ret = -ENOMEM;
> >                         goto out_unused_fd;
> >                 }
> > @@ -175,25 +167,22 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> >                         goto out_unused_fd;
> >                 }
> >
> > -               for (i = 0; i < exbuf->num_bo_handles; i++) {
> > -                       gobj = drm_gem_object_lookup(drm_file, bo_handles[i]);
> > -                       if (!gobj) {
> > -                               ret = -ENOENT;
> > -                               goto out_unused_fd;
> > -                       }
> > -
> > -                       qobj = gem_to_virtio_gpu_obj(gobj);
> > -                       buflist[i].bo = &qobj->tbo;
> > -
> > -                       list_add(&buflist[i].head, &validate_list);
> > +               buflist = virtio_gpu_array_from_handles(drm_file, bo_handles,
> > +                                                       exbuf->num_bo_handles);
> > +               if (!buflist) {
> > +                       ret = -ENOENT;
> > +                       goto out_unused_fd;
> >                 }
> >                 kvfree(bo_handles);
> >                 bo_handles = NULL;
> >         }
> >
> > -       ret = virtio_gpu_object_list_validate(&ticket, &validate_list);
> > -       if (ret)
> > -               goto out_free;
> > +       if (buflist) {
> > +               ret = drm_gem_lock_reservations(buflist->objs, buflist->nents,
> > +                                               &ticket);
> > +               if (ret)
> > +                       goto out_unused_fd;
> > +       }
> >
> >         buf = memdup_user(u64_to_user_ptr(exbuf->command), exbuf->size);
> >         if (IS_ERR(buf)) {
> > @@ -219,25 +208,28 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
> >                 fd_install(out_fence_fd, sync_file->file);
> >         }
> >
> > +       if (buflist)
> > +               for (i = 0; i < exbuf->num_bo_handles; i++)
> > +                       reservation_object_add_excl_fence(buflist->objs[i]->resv,
> > +                                                         &out_fence->f);
> > +
> Another module can see the semi-initialized fence after this.  We
> should move this after virtio_gpu_cmd_submit.
>
> >         virtio_gpu_cmd_submit(vgdev, buf, exbuf->size,
> > -                             vfpriv->ctx_id, out_fence);
> > +                             vfpriv->ctx_id, buflist, out_fence);
> >
> > -       ttm_eu_fence_buffer_objects(&ticket, &validate_list, &out_fence->f);
> > -
> > -       /* fence the command bo */
> > -       virtio_gpu_unref_list(&validate_list);
> > -       kvfree(buflist);
> > +       if (buflist)
> > +               drm_gem_unlock_reservations(buflist->objs, buflist->nents,
> > +                                           &ticket);
> When virtio_gpu_cmd_submit progresses really fast, buflist might have
> been freed.
>
> >         return 0;
> >
> >  out_memdup:
> >         kfree(buf);
> >  out_unresv:
> > -       ttm_eu_backoff_reservation(&ticket, &validate_list);
> > -out_free:
> > -       virtio_gpu_unref_list(&validate_list);
> > +       if (buflist)
> > +               drm_gem_unlock_reservations(buflist->objs, buflist->nents, &ticket);
> >  out_unused_fd:
> >         kvfree(bo_handles);
> > -       kvfree(buflist);
> > +       if (buflist)
> > +               virtio_gpu_array_put_free(buflist);
> >
> >         if (out_fence_fd >= 0)
> >                 put_unused_fd(out_fence_fd);
> > diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
> > index 6c1a90717535..0c87c3e086f8 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_vq.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
> > @@ -191,7 +191,7 @@ void virtio_gpu_dequeue_ctrl_func(struct work_struct *work)
> >         } while (!virtqueue_enable_cb(vgdev->ctrlq.vq));
> >         spin_unlock(&vgdev->ctrlq.qlock);
> >
> > -       list_for_each_entry_safe(entry, tmp, &reclaim_list, list) {
> > +       list_for_each_entry(entry, &reclaim_list, list) {
> >                 resp = (struct virtio_gpu_ctrl_hdr *)entry->resp_buf;
> >
> >                 trace_virtio_gpu_cmd_response(vgdev->ctrlq.vq, resp);
> > @@ -218,14 +218,18 @@ void virtio_gpu_dequeue_ctrl_func(struct work_struct *work)
> >                 }
> >                 if (entry->resp_cb)
> >                         entry->resp_cb(vgdev, entry);
> > -
> > -               list_del(&entry->list);
> > -               free_vbuf(vgdev, entry);
> >         }
> >         wake_up(&vgdev->ctrlq.ack_queue);
> >
> >         if (fence_id)
> >                 virtio_gpu_fence_event_process(vgdev, fence_id);
> > +
> > +       list_for_each_entry_safe(entry, tmp, &reclaim_list, list) {
> > +               if (entry->objs)
> > +                       virtio_gpu_array_put_free(entry->objs);
> > +               list_del(&entry->list);
> > +               free_vbuf(vgdev, entry);
> > +       }
> >  }
> >
> >  void virtio_gpu_dequeue_cursor_func(struct work_struct *work)
> > @@ -939,7 +943,9 @@ void virtio_gpu_cmd_transfer_from_host_3d(struct virtio_gpu_device *vgdev,
> >
> >  void virtio_gpu_cmd_submit(struct virtio_gpu_device *vgdev,
> >                            void *data, uint32_t data_size,
> > -                          uint32_t ctx_id, struct virtio_gpu_fence *fence)
> > +                          uint32_t ctx_id,
> > +                          struct virtio_gpu_object_array *objs,
> > +                          struct virtio_gpu_fence *fence)
> >  {
> >         struct virtio_gpu_cmd_submit *cmd_p;
> >         struct virtio_gpu_vbuffer *vbuf;
> > @@ -949,6 +955,7 @@ void virtio_gpu_cmd_submit(struct virtio_gpu_device *vgdev,
> >
> >         vbuf->data_buf = data;
> >         vbuf->data_size = data_size;
> > +       vbuf->objs = objs;
> >
> >         cmd_p->hdr.type = cpu_to_le32(VIRTIO_GPU_CMD_SUBMIT_3D);
> >         cmd_p->hdr.ctx_id = cpu_to_le32(ctx_id);
> > --
> > 2.18.1
> >