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

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

On 2015/2/2 20:19, Wei Liu wrote:
> On Mon, Feb 02, 2015 at 09:17:23AM +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.
> >
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> > ---
> > 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.
> My suggestion has one premise -- if upstream QEMU has already released
> that -gfx_passthru option. If there is no "old one" (in upstream QEMU)
> at all, then there is nothing to keep and deprecate.
Understood.

> >   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,
> Note this function is upstream QEMU specfic.
Yeah.

> >               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");
> >           }
> The comment contradicts what I know (or what I think I know). In our
> last email exchange you said there was no "-gfx_passthru" in any version
> of upstream QEMU.
>
> So, shouldn't you just remove this `if' statement?
Right. So what about this?

    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.

    Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index c2b0487..b888f19 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -701,9 +701,6 @@ static char ** 
libxl__build_device_model_args_new(libxl__gc *gc,
             flexarray_append(dm_args, "-net");
             flexarray_append(dm_args, "none");
         }
-        if (libxl_defbool_val(b_info->u.hvm.gfx_passthru)) {
-            flexarray_append(dm_args, "-gfx_passthru");
-        }
     } else {
         if (!sdl && !vnc) {
             flexarray_append(dm_args, "-nographic");
@@ -748,6 +745,11 @@ 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]);

Thanks
Tiejun

> Wei.
>
> > @@ -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]);
> > --
> > 1.9.1
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