On Thu, Oct 24, 2019 at 04:32:42PM +0800, Jason Wang wrote: > On 2019/10/24 下午4:03, Jason Wang wrote: > > On 2019/10/24 下午12:21, Tiwei Bie wrote: > > > On Wed, Oct 23, 2019 at 06:29:21PM +0800, Jason Wang wrote: > > > > On 2019/10/23 下午6:11, Tiwei Bie wrote: > > > > > On Wed, Oct 23, 2019 at 03:25:00PM +0800, Jason Wang wrote: > > > > > > On 2019/10/23 下午3:07, Tiwei Bie wrote: > > > > > > > On Wed, Oct 23, 2019 at 01:46:23PM +0800, Jason Wang wrote: > > > > > > > > On 2019/10/23 上午11:02, Tiwei Bie wrote: > > > > > > > > > On Tue, Oct 22, 2019 at 09:30:16PM +0800, Jason Wang wrote: > > > > > > > > > > On 2019/10/22 下午5:52, Tiwei Bie wrote: > > > > > > > > > > > This patch introduces a mdev based hardware vhost backend. > > > > > > > > > > > This backend is built on top of the same abstraction used > > > > > > > > > > > in virtio-mdev and provides a generic vhost interface for > > > > > > > > > > > userspace to accelerate the virtio devices in guest. > > > > > > > > > > > > > > > > > > > > > > This backend is implemented as a mdev device driver on top > > > > > > > > > > > of the same mdev device ops used in virtio-mdev but using > > > > > > > > > > > a different mdev class id, and it will register the device > > > > > > > > > > > as a VFIO device for userspace to use. Userspace can setup > > > > > > > > > > > the IOMMU with the existing VFIO container/group APIs and > > > > > > > > > > > then get the device fd with the device name. After getting > > > > > > > > > > > the device fd of this device, userspace can use vhost ioctls > > > > > > > > > > > to setup the backend. > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx> > > > > > > > > > > > --- > > > > > > > > > > > This patch depends on below series: > > > > > > > > > > > https://lkml.org/lkml/2019/10/17/286 > > > > > > > > > > > > > > > > > > > > > > v1 -> v2: > > > > > > > > > > > - Replace _SET_STATE with _SET_STATUS (MST); > > > > > > > > > > > - Check status bits at each step (MST); > > > > > > > > > > > - Report the max ring size and max number of queues (MST); > > > > > > > > > > > - Add missing MODULE_DEVICE_TABLE (Jason); > > > > > > > > > > > - Only support the network backend w/o multiqueue for now; > > > > > > > > > > Any idea on how to extend it to support > > > > > > > > > > devices other than net? I think we > > > > > > > > > > want a generic API or an API that could > > > > > > > > > > be made generic in the future. > > > > > > > > > > > > > > > > > > > > Do we want to e.g having a generic vhost > > > > > > > > > > mdev for all kinds of devices or > > > > > > > > > > introducing e.g vhost-net-mdev and vhost-scsi-mdev? > > > > > > > > > One possible way is to do what vhost-user does. I.e. Apart from > > > > > > > > > the generic ring, features, ... related ioctls, we also introduce > > > > > > > > > device specific ioctls when we need them. As vhost-mdev just needs > > > > > > > > > to forward configs between parent and userspace and even won't > > > > > > > > > cache any info when possible, > > > > > > > > So it looks to me this is only possible if we > > > > > > > > expose e.g set_config and > > > > > > > > get_config to userspace. > > > > > > > The set_config and get_config interface isn't really everything > > > > > > > of device specific settings. We also have ctrlq in virtio-net. > > > > > > Yes, but it could be processed by the exist API. Isn't > > > > > > it? Just set ctrl vq > > > > > > address and let parent to deal with that. > > > > > I mean how to expose ctrlq related settings to userspace? > > > > > > > > I think it works like: > > > > > > > > 1) userspace find ctrl_vq is supported > > > > > > > > 2) then it can allocate memory for ctrl vq and set its address through > > > > vhost-mdev > > > > > > > > 3) userspace can populate ctrl vq itself > > > I see. That is to say, userspace e.g. QEMU will program the > > > ctrl vq with the existing VHOST_*_VRING_* ioctls, and parent > > > drivers should know that the addresses used in ctrl vq are > > > host virtual addresses in vhost-mdev's case. > > > > > > That's really good point. And that means parent needs to differ vhost > > from virtio. It should work. > > > HVA may only work when we have something similar to VHOST_SET_OWNER which > can reuse MM of its owner. We already have VHOST_SET_OWNER in vhost now, parent can handle the commands in its .kick_vq() which is called by vq's .handle_kick callback. Virtio-user did something similar: https://github.com/DPDK/dpdk/blob/0da7f445df445630c794897347ee360d6fe6348b/drivers/net/virtio/virtio_user_ethdev.c#L313-L322 > > > > But is there any chance to use DMA address? I'm asking since the API > > then tends to be device specific. > > > I wonder whether we can introduce MAP IOMMU notifier and get DMA mappings > from that. I think this will complicate things unnecessarily and may bring pains. Because, in vhost-mdev, mdev's ctrl vq is supposed to be managed by host. And we should try to avoid putting ctrl vq and Rx/Tx vqs in the same DMA space to prevent guests having the chance to bypass the host (e.g. QEMU) to setup the backend accelerator directly. > > Thanks > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
