Re: [Qemu-devel] [v3][PATCH 2/2] libxl: introduce gfx_passthru_kind

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2015/3/27 17:54, Ian Campbell wrote:
> On Fri, 2015-03-27 at 09:29 +0800, Chen, Tiejun wrote:
>> On 2015/3/26 18:06, Ian Campbell wrote:
>>> On Thu, 2015-03-26 at 08:53 +0800, Chen, Tiejun wrote:
>>>>> Hrm, OK. I suppose we can live with autodetect and igd both meaning igd
>>>>> and whoever adds a new type will have to remember to add a check for
>>>>> qemu-trad then.
>>>>>
>>>>
>>>> When we really have to introduce a new type, this means we probably need
>>>> to change something inside qemu codes. So a new type should just go into
>>>> that table to support qemu upstream since now we shouldn't refactor
>>>> anything in qemu-xen-traditional, right?
>>>
>>> We'd want to error out on attempts to use qemu-xen-trad with non-IGD
>>> passthru.
>>>
>>
>> On qemu-xen-traditional side, we always recognize this as BOOLEAN,
>>
>>           if (libxl_defbool_val(b_info->u.hvm.gfx_passthru)) {
>>
>>               flexarray_append(dm_args, "-gfx_passthru");
>>
>>           }
>>
>> Additionally, this is also clarified explicitly in manpage, and
>> especially we don't change this behavior now, so I'm just wondering why
>> we should do this :)
>
> If someone does gfx_passthru = "foobar" and device_model_version =
> "qemu-xen-traditional" in their xl config then it would be rather mean
> of us to silently enable IGD passthru for them instead. When this occurs
> libxl should notice and fail.
>
> IGD is currently the only option, so this code would be needed when
> someone adds "foobar" support.
>

Sounds it should be a legacy fix to qemu-xen-tranditional :) So lets do 
it now,

@@ -326,6 +326,10 @@ static char ** 
libxl__build_device_model_args_old(libxl__gc *gc,
          }
          if (libxl_defbool_val(b_info->u.hvm.gfx_passthru)) {
              flexarray_append(dm_args, "-gfx_passthru");
+            if (b_info->u.hvm.gfx_passthru_kind >
+                                            LIBXL_GFX_PASSTHRU_KIND_IGD)
+                LOG(ERROR, "unsupported device type for 
\"gfx_passthru\".\n");
+                return NULL;
          }
      } else {
          if (!sdl && !vnc)


Thanks
Tiejun