[v3,1/2] libs/light: pass some infos to qemu

Commit Message

Manuel Bouyer Jan. 30, 2021, 11:02 p.m. UTC

Pass bridge name to qemu as command line option
When starting qemu, set an environnement variable XEN_DOMAIN_ID,
to be used by qemu helper scripts
The only functional difference of using the br parameter is that the
bridge name gets passed to the QEMU script.
NetBSD doesn't have the ioctl to rename network interfaces implemented, and
thus cannot rename the interface from tapX to vifX.Y-emu. Only qemu knowns
the tap interface name, so we need to use the qemu script from qemu itself.

Signed-off-by: Manuel Bouyer <[e-mail]>
Reviewed-by: Roger Pau Monné <[e-mail]>

---
 tools/libs/light/libxl_dm.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Ian Jackson Feb. 1, 2021, 2:56 p.m. UTC | #1

Manuel Bouyer writes ("[PATCH v3 1/2] libs/light: pass some infos to qemu"):
> Pass bridge name to qemu as command line option
> When starting qemu, set an environnement variable XEN_DOMAIN_ID,
> to be used by qemu helper scripts
> The only functional difference of using the br parameter is that the
> bridge name gets passed to the QEMU script.
> NetBSD doesn't have the ioctl to rename network interfaces implemented, and
> thus cannot rename the interface from tapX to vifX.Y-emu. Only qemu knowns
> the tap interface name, so we need to use the qemu script from qemu itself.
> 
> Signed-off-by: Manuel Bouyer <[e-mail]>
> Reviewed-by: Roger Pau Monné <[e-mail]>

I think this is a bugfix but it has implications for non-NetBSD
systems and I think it would be best for it to get (or not get) an
explicit release-ack.

I think it is sufficiently low risk to take it now.  We don't think
this will cause trouble for other platforms but if it proves to, that
should be fairly obvious and caught in our testing.  So:

Release-Acked-by: Ian Jackson <[e-mail]>

Ian.

Patch

diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
index 3da83259c0..13f79ec471 100644
--- a/tools/libs/light/libxl_dm.c
+++ b/tools/libs/light/libxl_dm.c
@@ -761,6 +761,8 @@  static int libxl__build_device_model_args_old(libxl__gc *gc,
         int nr_set_cpus = 0;
         char *s;
 
+        flexarray_append_pair(dm_envs, "XEN_DOMAIN_ID", GCSPRINTF("%d", domid));
+
         if (b_info->kernel) {
             LOGD(ERROR, domid, "HVM direct kernel boot is not supported by "
                  "qemu-xen-traditional");
@@ -1547,8 +1549,10 @@  static int libxl__build_device_model_args_new(libxl__gc *gc,
                 flexarray_append(dm_args, "-netdev");
                 flexarray_append(dm_args,
                                  GCSPRINTF("type=tap,id=net%d,ifname=%s,"
+                                           "br=%s,"
                                            "script=%s,downscript=%s",
                                            nics[i].devid, ifname,
+                                           nics[i].bridge,
                                            libxl_tapif_script(gc),
                                            libxl_tapif_script(gc)));
 
@@ -1825,6 +1829,8 @@  static int libxl__build_device_model_args_new(libxl__gc *gc,
     flexarray_append(dm_args, GCSPRINTF("%"PRId64, ram_size));
 
     if (b_info->type == LIBXL_DOMAIN_TYPE_HVM) {
+        flexarray_append_pair(dm_envs, "XEN_DOMAIN_ID", GCSPRINTF("%d", guest_domid));
+
         if (b_info->u.hvm.hdtype == LIBXL_HDTYPE_AHCI)
             flexarray_append_pair(dm_args, "-device", "ahci,id=ahci0");
         for (i = 0; i < num_disks; i++) {