On Thu, Jul 04, 2019 at 02:35:20PM +0800, Jason Wang wrote: > On 2019/7/4 下午2:21, Tiwei Bie wrote: > > On Thu, Jul 04, 2019 at 12:31:48PM +0800, Jason Wang wrote: > > > On 2019/7/3 下午9:08, Tiwei Bie wrote: > > > > On Wed, Jul 03, 2019 at 08:16:23PM +0800, Jason Wang wrote: > > > > > On 2019/7/3 下午7:52, Tiwei Bie wrote: > > > > > > On Wed, Jul 03, 2019 at 06:09:51PM +0800, Jason Wang wrote: > > > > > > > On 2019/7/3 下午5:13, Tiwei Bie wrote: > > > > > > > > Details about this can be found here: > > > > > > > > > > > > > > > > https://lwn.net/Articles/750770/ > > > > > > > > > > > > > > > > What's new in this version > > > > > > > > ========================== > > > > > > > > > > > > > > > > A new VFIO device type is introduced - vfio-vhost. This > > > > > > > > addressed > > > > > > > > some comments from > > > > > > > > here:https://patchwork.ozlabs.org/cover/984763/ > > > > > > > > > > > > > > > > Below is the updated device interface: > > > > > > > > > > > > > > > > Currently, there are two regions of this device: 1) > > > > > > > > CONFIG_REGION > > > > > > > > (VFIO_VHOST_CONFIG_REGION_INDEX), which can be used to setup the > > > > > > > > device; 2) NOTIFY_REGION (VFIO_VHOST_NOTIFY_REGION_INDEX), which > > > > > > > > can be used to notify the device. > > > > > > > > > > > > > > > > 1. CONFIG_REGION > > > > > > > > > > > > > > > > The region described by CONFIG_REGION is the main control > > > > > > > > interface. > > > > > > > > Messages will be written to or read from this region. > > > > > > > > > > > > > > > > The message type is determined by the `request` field in message > > > > > > > > header. The message size is encoded in the message header too. > > > > > > > > The message format looks like this: > > > > > > > > > > > > > > > > struct vhost_vfio_op { > > > > > > > > __u64 request; > > > > > > > > __u32 flags; > > > > > > > > /* Flag values: */ > > > > > > > > #define VHOST_VFIO_NEED_REPLY 0x1 /* Whether need reply */ > > > > > > > > __u32 size; > > > > > > > > union { > > > > > > > > __u64 u64; > > > > > > > > struct vhost_vring_state state; > > > > > > > > struct vhost_vring_addr addr; > > > > > > > > } payload; > > > > > > > > }; > > > > > > > > > > > > > > > > The existing vhost-kernel ioctl cmds are reused as the message > > > > > > > > requests in above structure. > > > > > > > Still a comments like V1. What's the advantage of inventing a new > > > > > > > protocol? > > > > > > I'm trying to make it work in VFIO's way.. > > > > > > > > > > > > > I believe either of the following should be better: > > > > > > > > > > > > > > - using vhost ioctl, we can start from > > > > > > > SET_VRING_KICK/SET_VRING_CALL and > > > > > > > extend it with e.g notify region. The advantages is that all > > > > > > > exist userspace > > > > > > > program could be reused without modification (or minimal > > > > > > > modification). And > > > > > > > vhost API hides lots of details that is not necessary to be > > > > > > > understood by > > > > > > > application (e.g in the case of container). > > > > > > Do you mean reusing vhost's ioctl on VFIO device fd directly, > > > > > > or introducing another mdev driver (i.e. vhost_mdev instead of > > > > > > using the existing vfio_mdev) for mdev device? > > > > > Can we simply add them into ioctl of mdev_parent_ops? > > > > Right, either way, these ioctls have to be and just need to be > > > > added in the ioctl of the mdev_parent_ops. But another thing we > > > > also need to consider is that which file descriptor the userspace > > > > will do the ioctl() on. So I'm wondering do you mean let the > > > > userspace do the ioctl() on the VFIO device fd of the mdev > > > > device? > > > > > > > Yes. > > Got it! I'm not sure what's Alex opinion on this. If we all > > agree with this, I can do it in this way. > > > > > Is there any other way btw? > > Just a quick thought.. Maybe totally a bad idea. > > > It's not for sure :)
Thanks! > > > > I was thinking > > whether it would be odd to do non-VFIO's ioctls on VFIO's device > > fd. So I was wondering whether it's possible to allow binding > > another mdev driver (e.g. vhost_mdev) to the supported mdev > > devices. The new mdev driver, vhost_mdev, can provide similar > > ways to let userspace open the mdev device and do the vhost ioctls > > on it. To distinguish with the vfio_mdev compatible mdev devices, > > the device API of the new vhost_mdev compatible mdev devices > > might be e.g. "vhost-net" for net? > > > > So in VFIO case, the device will be for passthru directly. And > > in VHOST case, the device can be used to accelerate the existing > > virtualized devices. > > > > How do you think? > > > If my understanding is correct, there will be no VFIO ioctl if we go for > vhost_mdev? Yeah, exactly. If we go for vhost_mdev, we may have some vhost nodes in /dev similar to what /dev/vfio/* does to handle the $UUID and open the device (e.g. similar to VFIO_GROUP_GET_DEVICE_FD in VFIO). And to setup the device, we can try to reuse the ioctls of the existing kernel vhost as much as possible. Thanks, Tiwei > > Thanks > > > > > > Thanks, > > Tiwei > > > Thanks > > >
