I think GP meant to say (the extremely confusingly named) virtio-fs, as opposed to virtfs/9pvirtio.
Virtio-fs is independent of 9P and has optional support for using shared memory to greatly increase performance, it also maps better to the permissions and metadata of "modern" filesystems IIRC, not sure if 9pvirtio had this problem but I remember coworkers having permissions problems with the 9P bridge in WSL2 (Plan9's permission system is very simple and doesn't map well to other VFS's)
> Plan9's permission system is very simple and doesn't map well to other VFS's
Plan 9 is a pure VFS OS. 9p uses regular unix permissions which map just fine. The major issue is that since plan 9 is all vfs, there are no crufty unix leftovers like hidden dot files or hard/soft links. User specific configuration files belong in $user/lib and bind replaces hacky links. These old unix hacks were accommodated in 9p2000.u. Further extensions to .u resulted in 9p2000.L which adds some Linux metadata stuff (I cant remember right now, my memory of 9p2000.u/L is fading).
Virtio-fs is independent of 9P and has optional support for using shared memory to greatly increase performance, it also maps better to the permissions and metadata of "modern" filesystems IIRC, not sure if 9pvirtio had this problem but I remember coworkers having permissions problems with the 9P bridge in WSL2 (Plan9's permission system is very simple and doesn't map well to other VFS's)