On Fri, Jul 05, 2019 at 08:49:46AM -0600, Alex Williamson wrote: > On Thu, 4 Jul 2019 14:21:34 +0800 > Tiwei Bie <tiwei.bie@xxxxxxxxx> 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. 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? > > VFIO really can't prevent vendor specific ioctls on the device file > descriptor for mdevs, but a) we'd want to be sure the ioctl address > space can't collide with ioctls we'd use for vfio defined purposes and > b) maybe the VFIO user API isn't what you want in the first place if > you intend to mostly/entirely ignore the defined ioctl set and replace > them with your own. In the case of the latter, you're also not getting > the advantages of the existing VFIO userspace code, so why expose a > VFIO device at all. Yeah, I totally agree. > > The mdev interface does provide a general interface for creating and > managing virtual devices, vfio-mdev is just one driver on the mdev > bus. Parav (Mellanox) has been doing work on mdev-core to help clean > out vfio-isms from the interface, aiui, with the intent of implementing > another mdev bus driver for using the devices within the kernel. Great to know this! I found below series after some searching: https://lkml.org/lkml/2019/3/8/821 In above series, the new mlx5_core mdev driver will do the probe by calling mlx5_get_core_dev() first on the parent device of the mdev device. In vhost_mdev, maybe we can also keep track of all the compatible mdev devices and use this info to do the probe. But we also need a way to allow vfio_mdev driver to distinguish and reject the incompatible mdev devices. > It > seems like this vhost-mdev driver might be similar, using mdev but not > necessarily vfio-mdev to expose devices. Thanks, Yeah, I also think so! Thanks! Tiwei > > Alex _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
