Re: [Qemu-devel] [v2][PATCH] libxl: add one machine property to support IGD GFX passthrough

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

On 2015/2/2 19:08, Ian Campbell wrote:
> On Mon, 2015-02-02 at 09:17 +0800, Tiejun Chen wrote:
>> When we're working to support IGD GFX passthrough with qemu
>> upstream, instead of "-gfx_passthru" we'd like to make that
>> a machine option, "-machine xxx,-igd-passthru=on". This need
>> to bring a change on tool side.
>
>>From which Qemu version is this new option accepted? What will a verison
> of qemu prior to then do when presented with the new option?

Sorry, maybe I'm not describing this correctly.

Actually qemu upstream never own this option, '-gfx_passthru' at all. 
This just exists alone in qemu-xen-traditional. So here I'm trying to 
introduce a new stuff that doesn't clash anything in qemu upstream.

So I guess I should rephrase this as follows:

     libxl: add one machine property to support IGD GFX passthrough

     When we're working to support IGD GFX passthrough with qemu
     upstream, we'd like to introduce a machine option,
     "-machine xxx,igd-passthru=on", to enable/disable that feature.
     And we also remove that old option, "-gfx_passthru", just from
     the case of LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN since actually
     no any qemu stream version really need or use that.

>
> (nb: you have an extra '-' in the description I think)

Yeah, I will remove that.

Thanks
Tiejun

>
>>
>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>> ---
>> v2:
>>
>> * Based on some discussions with Wei we'd like to keep both old
>>    option, -gfx_passthru, and new machine property option,
>>    "-machine xxx,-igd-passthru=on" at the same time but deprecate
>>    the old one. Then finally we remove the old one at that point
>>    that to give downstream (in this case, Xen) time to cope with the
>>    change.
>>
>>   tools/libxl/libxl_dm.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
>> index c2b0487..8405f0b 100644
>> --- a/tools/libxl/libxl_dm.c
>> +++ b/tools/libxl/libxl_dm.c
>> @@ -701,6 +701,11 @@ static char ** libxl__build_device_model_args_new(libxl__gc *gc,
>>               flexarray_append(dm_args, "-net");
>>               flexarray_append(dm_args, "none");
>>           }
>> +        /*
>> +         * Although we already introduce 'igd-passthru', but we'd like
>> +         * to remove this until we give downstream time to cope with
>> +         * the change.
>> +         */
>>           if (libxl_defbool_val(b_info->u.hvm.gfx_passthru)) {
>>               flexarray_append(dm_args, "-gfx_passthru");
>>           }
>> @@ -748,6 +753,11 @@ static char ** libxl__build_device_model_args_new(libxl__gc *gc,
>>                                               machinearg, max_ram_below_4g);
>>               }
>>           }
>> +
>> +        if (libxl_defbool_val(b_info->u.hvm.gfx_passthru)) {
>> +            machinearg = libxl__sprintf(gc, "%s,igd-passthru=on", machinearg);
>> +        }
>> +
>>           flexarray_append(dm_args, machinearg);
>>           for (i = 0; b_info->extra_hvm && b_info->extra_hvm[i] != NULL; i++)
>>               flexarray_append(dm_args, b_info->extra_hvm[i]);
>
>
>