Re: [Qemu-devel] [PULL 09/36] 9p: simplify source file selection

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

Hi Paolo,

On 8/20/19 8:59 AM, Paolo Bonzini wrote:
> Express the complex conditions in Kconfig rather than Makefiles, since Kconfig
> is better suited at expressing dependencies and detecting contradictions.
> 
> Cc: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
>  Kconfig.host        | 1 +
>  fsdev/Makefile.objs | 2 +-
>  hw/9pfs/Kconfig     | 5 +++++
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/Kconfig.host b/Kconfig.host
> index aec9536..bb6e116 100644
> --- a/Kconfig.host
> +++ b/Kconfig.host
> @@ -28,6 +28,7 @@ config VHOST_USER
>  
>  config XEN
>      bool
> +    select FSDEV_9P if VIRTFS

There is something odd with CONFIG_XEN, as it is used
to select accelerator and hardware.

>  
>  config VIRTFS
>      bool
> diff --git a/fsdev/Makefile.objs b/fsdev/Makefile.objs
> index 24bbb3e..42cd70c 100644
> --- a/fsdev/Makefile.objs
> +++ b/fsdev/Makefile.objs
> @@ -1,6 +1,6 @@
>  # Lots of the fsdev/9pcode is pulled in by vl.c via qemu_fsdev_add.
>  # only pull in the actual 9p backend if we also enabled virtio or xen.
> -ifeq ($(call land,$(CONFIG_VIRTFS),$(call 
> lor,$(CONFIG_VIRTIO_9P),$(CONFIG_XEN))),y)
> +ifeq ($(CONFIG_FSDEV_9P),y)
>  common-obj-y = qemu-fsdev.o 9p-marshal.o 9p-iov-marshal.o
>  else
>  common-obj-y = qemu-fsdev-dummy.o
> diff --git a/hw/9pfs/Kconfig b/hw/9pfs/Kconfig
> index 8c5032c..3ae5749 100644
> --- a/hw/9pfs/Kconfig
> +++ b/hw/9pfs/Kconfig
> @@ -1,4 +1,9 @@
> +config FSDEV_9P
> +    bool
> +    depends on VIRTFS

Using "depends on VIRTFS && 9PFS" instead helps to
reduce the link failure using --without-default-devices.

> +
>  config VIRTIO_9P
>      bool
>      default y
>      depends on VIRTFS && VIRTIO
> +    select FSDEV_9P

Here I used "depends on FSDEV_9P && VIRTIO" but this
doesn't look right...

Is it possible to include "config-devices.h" in
hw/xen/xen-legacy-backend.c to use CONFIG_9PFS?

xen_be_register_common() unconditionally calls:

  xen_be_register("9pfs", &xen_9pfs_ops);

As I have no much idea about Xen & 9pfs, I'm a bit
lost here (regarding the dependencies order).

Thanks,

Phil.