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

From: Chen, Tiejun
Subject: Re: [Qemu-devel] [v2][PATCH] libxl: add one machine property to support IGD GFX passthrough
Date: Tue, 03 Feb 2015 09:00:04 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0

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.


Signed-off-by: Tiejun Chen <address@hidden>

* 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

  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]);

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