Messages in this thread | | | Subject | Re: [RFC v2] vhost: introduce mdev based hardware vhost backend | From | Jason Wang <> | Date | Thu, 4 Jul 2019 12:31:48 +0800 |
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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. Is there any other way btw?
Thanks
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