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

[Stefan Hajnoczi]

On Mon, Nov 16, 2020 at 07:59:27PM +0100, Jonas Andradas wrote:
> On Mon, Nov 16, 2020 at 12:36 PM Jonathan Watt <jwatt at jwatt.org> wrote:

CCing Gal Hammer regarding the Windows virtio-fs drivers.

When you find a solution we can update the howto. Pull requests for
making changes to the website can be sent here:
https://gitlab.com/virtio-fs/virtio-fs.gitlab.io

> 
> > 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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