Re: [PATCH] qemu-options.hx: 9p: clarify -virtfs vs. -fsdev

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Dienstag, 31. März 2020 17:27:27 CEST Cornelia Huck wrote:
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 962a5ebaa6..fd3830c6cd 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -1542,9 +1542,17 @@ SRST
> > 
> >  ``-virtfs proxy,sock_fd=sock_fd,mount_tag=mount_tag
> >  [,writeout=writeout][,readonly]``>  
> >    \
> >  
> >  ``-virtfs synth,mount_tag=mount_tag``
> > 
> > -    Define a new filesystem device and expose it to the guest using a
> > -    virtio-9p-device. The general form of a Virtual File system
> > -    pass-through options are:
> > +    Define a new virtual filesystem device and expose it to the guest
> > using +    a virtio-9p-device (a.k.a. 9pfs), which essentially means that
> > a certain +    directory on host is made directly accessible by guest as
> > a pass-through +    file system by using the 9P network protocol for
> > communication between +    host and guests, if desired even accessible,
> > shared by several guests +    simultaniously.
> > +
> > +    Note that ``-virtfs`` is actually just a convenience shortcut for its
> > +    generalized form ``-fsdev -device virtio-9p-pci``.
> 
> Huh. This prompted me to try this on s390, and it actually creates a
> virtio-9p-pci device there as well, not a virtio-9p-ccw device. A bit
> surprising; but I don't see 9p used much (if at all) on s390 anyway.

Yeah, "virtio-9p-pci" is currently hard coded in softmmu/vl.c [line 3352]:
https://github.com/qemu/qemu/blob/17083d6d1e0635371418c26b613a6fa68d392f49/softmmu/vl.c#L3352

> > +
> > 
> > +    The general form of pass-through file system options are:
> >      ``local``
> >      
> >          Accesses to the filesystem are done by QEMU.
> 
> Good to see this spelled out:
> 
> Acked-by: Cornelia Huck <cohuck@redhat.com>

Best regards,
Christian Schoenebeck