[Virtio-fs] Issues with the virtio-fs Windows how-to (unexpected read-only file system)

[Jonas Andradas]

On Mon, Nov 16, 2020 at 12:36 PM Jonathan Watt <jwatt at jwatt.org> wrote:

> Hello list,
>
> Thank you all for your work on virtio-fs. It's a very exciting step
> forward!
>
> Like others[1], I've encountered the issue where virtio-fs mounted file
> systems
> are unexpectedly read-only/inaccessible on Windows.
>
> I worked through the Windows how-to page[2], but the "Installing the
> virtio-fs
> service" instructions at the bottom did not work for me, as written. The
> instructions are to set the new `VirtioFsSvc` service to depend on both
> `WinFsp.Launcher` and `VirtioFsDrv`. However, like others, I found that
> the new
> service would not run since `VirtioFsDrv` does not appear to exist (be a
> service).
>
>
I too did not manage this to work, and initially removed any dependencies,
thus resulting in the same behaviour you mention.


> After opening `regedit`, opening the key:
>
>   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VirtioFsSvc
>
> removing `VirtioFsDrv` from the value of `DependsOnService`, and then
> restarting
> the `VirtioFsSvc` service, the file system shared via virtio-fs appeared at
> 'Z:\' and worked as expected. However, this only works until the Windows
> VM is
> rebooted.
>
> On rebooting the Windows VM, the shared file system becomes read-only and
> its
> sub-directories cannot be opened. Manually restarting the `VirtioFsSvc`
> service
> gets the share working again (until next reboot). This seems to indicate
> that
> `VirtioFsSvc` is running too early, and that it really does need to wait
> for
> *something* else to be ready before starting.
>
> I suppose the first question is what is `VirtioFsDrv` and where is it
> supposed
>
to come from? Are there steps missing from the Windows how-to or has the
> name of
> this service changed?
>
>
I checked the Virtio FS driver, both from the Device Manager (Properties
and then checking the "Service" name associated with it) and also using the
"driverquery" command.  Based on this, I modified the service to depend
both on WinFps.Launcher and this driver ("VirtFS") by issuing the following
command:

sc.exe config VirtioFSsvc depend= WinFsp.Launcher/VirtFS

However, so far I have not had better results than you, as when I reboot I
still have the shared folder as read-only, and only restarting the service
manually fixes it.

I have tried different combinations by adding all the drivers I saw which
could be involved (although unlikely, but just in case), resulting in
dependencies such as:

sc.exe config VirtioFSsvc depend=
WinFsp.Launcher/VirtFS/vioscsi/viostor/VirtioSerial/WinFsp

But, still, to no avail.


> -Jonathan
>
> 1. For example, the comments starting here:
>
> https://github.com/virtio-win/kvm-guest-drivers-windows/issues/473#issuecomment-658379853
>
> 2. https://virtio-fs.gitlab.io/howto-windows.html
>
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