New VM kernel option needed in Parallels Desktop for Mac 26.1.1

[RyanM45]

I just got the update to Parallels Desktop for Mac v26.1.1 and tried to install the VM tools package in my VM. I use an ARM64 install of Gentoo Linux in my Parallels VM. I know Gentoo isn't directly supported. I saw in the VM release notes that the Parallels tools no longer needed a kernel module. This is great! But I was disappointed that I wasn't able to see my Shared VM folders anymore. After some troubleshooting, I came upon the problem and found the solution. Running some of the Parallels tools in Linux using strace I was able to see them try to open a socket using AF_VSOCK. That's something called a "VM Socket" which I guess is used to communicate with the VM presumably so it can get the Shared Folder configuration. I had never heard of that kernel option before.
If you compile your own Linux kernel, that option is called VIRTIO_SOCKETS and is configured under the kernel source menuconfig at Network Support -> Networking Options -> Virtual Socket protocol -> virtio transport for Virtual Sockets. If compiled as a module, the module is called vmv_vsock_virtio_transport. You'll have to make sure that module is loaded.
Once I had that option enabled in my kernel and loaded the module, my shared folders came back.

 

[ParallelsU1069]

Good to hear you experience with the new Parallels Tools available in Parallels 26.1.1. I've been looking for more information as to what changes were made and how the new Parallels Tools for Linux works but there seems to be no information available yet on the Parallels KB or forums other than "Introduces the new, driverless version of Parallels Tools for Linux, designed to minimize installation and kernel compatibility issues." from the 26.1.1 release notes. The only information I can gather at the moment is that VirtioVsock is being used and a kernel module is no longer required.

Please post a link(s) if anyone is aware of how the new 26.1.1 Parallels Tools (for Linux) works and/or what changes were made. Thanks.

 

[RyanM45]

From what I can see, the Parallels Tools for Linux seem to be mostly the same. There's still a time sync daemon (prltimesync) launched by the Parallels tools daemon (prltoolsd). Mounting the shared folders in the Linux guest seems to work mostly the same as well using a tool implemented with the FUSE framework. (prl_fsd) I think what changed is that the Parallels "tools gate driver" that was a kernel module is now gone. I guess they were able to find other ways to implement whatever hooks the Tools Gate driver was doing before. And clearly using the Virtio VM socket driver is part of the implementation change.
When I first installed the new Parallels Tools on my Linux Guest I wasn't getting the Shared Folders to mount. I started looking through the scripts in the Tools package. I eventually came across a call to a tool called prl_showvmcfg which seemed to be used to get the Shared Folders configuration from the VM. Clearly that tool wasn't working for me anymore so I ran it using the strace utility which is used to dump which system calls a program is calling. I saw a failure when the tool tried to create a VM socket so that was my clue that my guest didn't support that function. After I added a module to add support for the VM socket (as mentioned in my first post) then I got my shared folders mounted again.
The Parallels Tools implementation looks mostly the same except for them finding alternative ways to implement whatever functionality the Tools Driver was doing before.