[Virtio-fs] Mount several mount tags in Windows using VirtioFS

[Jonas Andradas]

Hi Gal,

On Tue, Nov 3, 2020 at 5:32 PM Gal Hammer <ghammer at redhat.com> wrote:

> Hi Jonas,
>
> On Tue, 3 Nov 2020 at 18:15, Jonas Andradas <j.andradas at gmail.com> wrote:
>
>> Hello,
>>
>> TL;DR - Is there a way to mount more than one filesystem from a Linux
>> host inside a Windows guest using VirtioFS?
>>
>
> TL;DR No.
>
>
Thanks for the information/confirmation!


> I didn't implement (yet?) the code to track all the instances of PCI
> devices and mount a folder or a drive for each one.
>
>
For the moment, I will mount a temporary folder from the host and copy
to/from it the files as needed.  My first approach to work around this was
to create symbolic links within this shared folder, to the directories I
wanted to share, but Windows sees the symbolic links (1 KB files) rather
than following the link and thus being able to access the 2 or 3 different
host directories by mounting just one.

I have a Windows guest running on a Linux host, and I wanted to share
>> several directories from the host inside the guest using VirtioFS.
>>
>> I followed the instructions I found in several places [1][2][3], and have
>> installed the VirtioFS drivers and WinFPS. I first tried with one
>> filesystem, and I can mount it and browse it fine.
>>
>> I then configured my Windows guest XML definition so it has 2
>> 'filesystems' to, each with its own mount_tag (e.g. 'software' for
>> '/home/user/software' and 'documents' for '/home/user/documents').  Windows
>> shows 2 "Virtio FS Devices" in the device manager, so this looks promising.
>>
>> However, when I run 'virtiofs.exe' within Windows (or the service [1]
>> suggests starts), I get a "Z:" mount (or whichever letter I specify with
>> '-m <DRIVE>') with the first filesystem I specified ('software' in the
>> example above).  If I then run 'virtiofs.exe' for a second time, I get a
>> new mount (e.g. Y:), but with the same filesystem ('software', and not
>> 'documents').
>>
>> I tried adding the mount_tag to the virtiofs.exe command line, or even
>> the PCI path Windows sees the devices on, but this fails (understandably
>> so, since the help does not indicate how to specify which filesystem should
>> be mounted).
>>
>> My question was whether (and if so, how) it is actually possible to mount
>> more than one directory from the host inside a Windows guest using VirtioFS
>> (as can be done in Linux guests).
>>
>> [1] https://virtio-fs.gitlab.io/howto-windows.html
>> [2]
>> https://github.com/virtio-win/kvm-guest-drivers-windows/issues/126#issuecomment-667432487
>> [3]
>> https://www.reddit.com/r/VFIO/comments/i12uyn/virtiofs_is_amazing_plus_how_i_set_it_up/g12o5qt/
>>
>> (...)
>>
>>
>     Gal.
>

Cheers,
Jonas.
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