Ubuntu
rust-virtiofsd package

Guest VM access to shared directories hangs with virtiofsd 1.7.0

Asked by B

I have a computer running ubuntu, and VMs within it that access host directories via virtiofsd. I recently went through a distribution upgrade and experienced the following:
1) After upgrading to mantic, the VMs could not start up because virtiofsd was not found
2) I ran `apt install virtiofsd` on the host. This installed version 1.7.0 from the ubuntu repository.
3) The VMs then restarted, but any attempt to access the shared directory from the guest resulted in a guest process hang.
4) This was solved by running `apt remove virtiofsd`, downloading release 1.8.0 from virtiofsd's github, and doing a local build + install.

What I would have expected
1) Things should have just continue working as they did prior to the distribution upgrade.
2) If somehow installing virtiofsd manually needed to be done, then I would've expected the installed version to work instead of causing guest processes to hang.

My specific problem is solved so I no longer have a way to reproduce the issue. Is there anything that I can help provide to understand what might have happened, or to help others similarly afflicted to find the solution?

Thanks.

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B
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Revision history for this message
Manfred Hampl (m-hampl) said : 		#1

"After upgrading to mantic"
From which release did you upgrade to mantic?

"because virtiofsd was not found"
The virtiofsd package was only introduced with Ubuntu mantic.
So the question is: What did you have before (and from which source)?

Revision history for this message
B (oo187w) said : 		#2

> From which release did you upgrade to mantic?

From Kinetic Kudu.

> The virtiofsd package was only introduced with Ubuntu mantic.
> So the question is: What did you have before (and from which source)?

I am guessing that I had got it from qemu-system-common. I don't recall adding package repos to my installation.

To confirm:
* I downloaded the deb file listed at https://answers.launchpad.net/ubuntu/kinetic/amd64/qemu-system-common/1:7.0+dfsg-7ubuntu2.6 and its contents, listed with dpkg-deb --contents, include /usr/share/qemu/vhost-user/50-qemu-virtiofsd.json and /usr/lib/qemu/virtiofsd.
* I checked my current qemu-system-common package (1:8.0.4+dfsg-1ubuntu3), and its contents listed with dpkg -L do not include these files.

Revision history for this message
Manfred Hampl (m-hampl) said : 		#3

Did you upgrade directly from kinetic to mantic, skipping lunar?

In the change log of qemu 1.8 there is a note
"d/qemu-system-common.NEWS: document dropping of virtiofsd"

Revision history for this message
B (oo187w) said : 		#4

> Did you upgrade directly from kinetic to mantic, skipping lunar?

My bad, it looks like I upgraded from kinetic to lunar first (which didn't introduce any problems) and then from lunar to mantic.

Sounds like one of the problems I encountered (virtiofsd dropping due to the upgrade) was expected. I'm not sure if the other problem (guest processes hanging on attempts to access host shares via virtiofs) is a bug but hopefully if someone comes across this same issue they may give a shot to building a later version of virtiofsd and see if it works for them.