Jason Wang
2021-Jul-02 03:25 UTC
[PATCH v8 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace
? 2021/7/1 ??6:26, Yongji Xie ??:> On Thu, Jul 1, 2021 at 3:55 PM Jason Wang <jasowang at redhat.com> wrote: >> >> ? 2021/7/1 ??2:50, Yongji Xie ??: >>> On Wed, Jun 30, 2021 at 5:51 PM Stefan Hajnoczi <stefanha at redhat.com> wrote: >>>> On Tue, Jun 29, 2021 at 10:59:51AM +0800, Yongji Xie wrote: >>>>> On Mon, Jun 28, 2021 at 9:02 PM Stefan Hajnoczi <stefanha at redhat.com> wrote: >>>>>> On Tue, Jun 15, 2021 at 10:13:30PM +0800, Xie Yongji wrote: >>>>>>> +/* ioctls */ >>>>>>> + >>>>>>> +struct vduse_dev_config { >>>>>>> + char name[VDUSE_NAME_MAX]; /* vduse device name */ >>>>>>> + __u32 vendor_id; /* virtio vendor id */ >>>>>>> + __u32 device_id; /* virtio device id */ >>>>>>> + __u64 features; /* device features */ >>>>>>> + __u64 bounce_size; /* bounce buffer size for iommu */ >>>>>>> + __u16 vq_size_max; /* the max size of virtqueue */ >>>>>> The VIRTIO specification allows per-virtqueue sizes. A device can have >>>>>> two virtqueues, where the first one allows up to 1024 descriptors and >>>>>> the second one allows only 128 descriptors, for example. >>>>>> >>>>> Good point! But it looks like virtio-vdpa/virtio-pci doesn't support >>>>> that now. All virtqueues have the same maximum size. >>>> I see struct vpda_config_ops only supports a per-device max vq size: >>>> u16 (*get_vq_num_max)(struct vdpa_device *vdev); >>>> >>>> virtio-pci supports per-virtqueue sizes because the struct >>>> virtio_pci_common_cfg->queue_size register is per-queue (controlled by >>>> queue_select). >>>> >>> Oh, yes. I miss queue_select. >>> >>>> I guess this is a question for Jason: will vdpa will keep this limitation? >>>> If yes, then VDUSE can stick to it too without running into problems in >>>> the future. >> >> I think it's better to extend the get_vq_num_max() per virtqueue. >> >> Currently, vDPA assumes the parent to have a global max size. This seems >> to work on most of the parents but not vp-vDPA (which could be backed by >> QEMU, in that case cvq's size is smaller). >> >> Fortunately, we haven't enabled had cvq support in the userspace now. >> >> I can post the fixes. >> > OK. If so, it looks like we need to support the per-vq configuration. > I wonder if it's better to use something like: VDUSE_CREATE_DEVICE -> > VDUSE_SETUP_VQ -> VDUSE_SETUP_VQ -> ... -> VDUSE_ENABLE_DEVICE to do > initialization rather than only use VDUSE_CREATE_DEVICE.This should be fine. Thanks> > Thanks, > Yongji >