Re: [Qemu-devel] [PATCH v2] 9pfs: fix dependencies

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 9 Aug 2017 11:07:38 +0200
Thomas Huth <thuth@redhat.com> wrote:

> On 09.08.2017 10:27, Cornelia Huck wrote:
> > On Wed, 9 Aug 2017 10:23:04 +0200
> > Thomas Huth <thuth@redhat.com> wrote:
> >   
> >> On 09.08.2017 09:17, Cornelia Huck wrote:  
> >>> Nothing in fsdev/ or hw/9pfs/ depends on pci; it should rather depend
> >>> on CONFIG_VIRTFS and on the presence of an appropriate virtio transport
> >>> device.
> >>>
> >>> Let's introduce CONFIG_VIRTIO_CCW to cover s390x and check for
> >>> CONFIG_VIRTFS && (CONFIG_VIRTIO_PCI || CONFIG_VIRTIO_CCW).
> >>>
> >>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> >>> ---
> >>>
> >>> Changes v1->v2: drop extraneous spaces, fix build on cris
> >>>
> >>> ---
> >>>  default-configs/s390x-softmmu.mak | 1 +
> >>>  fsdev/Makefile.objs               | 9 +++------
> >>>  hw/Makefile.objs                  | 2 +-
> >>>  3 files changed, 5 insertions(+), 7 deletions(-)  
> [...]
> >>
> >> Patch should be fine now, I think...
> >>
> >> But thinking about this again, I wonder whether it would be enough to
> >> simply check for CONFIG_VIRTIO=y here instead. CONFIG_VIRTIO=y should be
> >> sufficient to assert that there is also at least one kind of virtio
> >> transport available, right?
> >> Otherwise this will look really horrible as soon as somebody also tries
> >> to add support for virtio-mmio here later ;-)  
> > 
> > Do all virtio transports have support for 9p, though? I thought it was
> > only virtio-pci and virtio-ccw...  
> 
> While virtio-pci and virtio-ccw seem to require separate dedicated
> devices (e.g. virtio-9p-pci and virtio-9p-ccw) for everything,
> virtio-mmio seems to work different. As far as I can see, there are no
> dedicated virtio-xxx-mmio devices in the code at all. According to
> https://www.redhat.com/archives/libvir-list/2013-August/msg00009.html
> you simply have to use virtio-xxx-device here instead. And a
> virtio-9p-device is available. So theoretically, the 9p code should work
> with virtio-mmio, too, or is there a problem that I did not see yet?
> 
> Anyway, we likely should not blindly enable this, so unless somebody has
> a setup to test it, we should go with your current patch instead, I think.

Yes, I'd prefer if somebody with a virtio-mmio setup could chime in.

Given the current Makefiles, this cannot have worked for !pci anyway...