Re: [Qemu-devel] [RFC 1/4] [UNTESTED] xen: Don't force has_dynamic_sysbus on machine class

[Juergen Gross <jgross@suse.com>]

On 23/03/17 22:28, Eduardo Habkost wrote:
> The xen-backend devices created by the Xen code are not supposed
> to be treated as dynamic sysbus devices. This is an attempt to
> change that and see what happens, but I couldn't test it because
> I don't have a Xen host set up.
> 
> If this patch breaks anything, this means we have a bug in
> foreach_dynamic_sysbus_device(), which is supposed to return only
> devices created using -device.
> 
> The original code that sets has_dynamic_sysbus was added by
> commit 3a6c9172ac5951e6dac2b3f6cbce3cfccdec5894, but I don't see
> any comment explaining why it was necessary.

xen-backend devices are created via qmp commands when attaching new
pv-devices to a domain. They can be dynamically removed, too. Setting
has_dynamic_sysbus was necessary to support this feature.

So just removing it will break Xen.

NAK as a standalone patch.


Juergen

> 
> Cc: Juergen Gross <jgross@suse.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  hw/xen/xen_backend.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
> index 6c21c37d68..4607d6d3ee 100644
> --- a/hw/xen/xen_backend.c
> +++ b/hw/xen/xen_backend.c
> @@ -550,15 +550,6 @@ err:
>      return -1;
>  }
>  
> -static void xen_set_dynamic_sysbus(void)
> -{
> -    Object *machine = qdev_get_machine();
> -    ObjectClass *oc = object_get_class(machine);
> -    MachineClass *mc = MACHINE_CLASS(oc);
> -
> -    mc->has_dynamic_sysbus = true;
> -}
> -
>  int xen_be_register(const char *type, struct XenDevOps *ops)
>  {
>      char path[50];
> @@ -580,8 +571,6 @@ int xen_be_register(const char *type, struct XenDevOps *ops)
>  
>  void xen_be_register_common(void)
>  {
> -    xen_set_dynamic_sysbus();
> -
>      xen_be_register("console", &xen_console_ops);
>      xen_be_register("vkbd", &xen_kbdmouse_ops);
>      xen_be_register("qdisk", &xen_blkdev_ops);
>