[libvirt] [PATCH] libvirt: xen: do not use ioemu type for any emulated NIC

[Stefan Bader]

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When using the xm/xend stack to manage instances there is a bug that causes
the emulated interfaces to be unusable when the vif config contains type=ioemu.

The current code already has a special quirk to not use this keyword if no
specific model is given for the emulated NIC (defaulting to rtl8139).
Essentially it works because regardless of the type argument, the Xen stack
always creates emulated and paravirt interfaces and lets the guest decide
which one to use. So neither xl nor xm stack actually require the type keyword
for emulated NICs.

- ---
/*
 * apparently type ioemu breaks paravirt drivers on HVM so skip this
 * from XEND_CONFIG_MAX_VERS_NET_TYPE_IOEMU
 */
 if (xendConfigVersion <= XEND_CONFIG_MAX_VERS_NET_TYPE_IOEMU)
     virBufferAddLit(&buf, ",type=ioemu");
- ---

This is still broken when a different emulated NIC (eg. e1000 is enforced),
but the same fix solves that problem. Which is what the attached patch does.

I have been testing with this change applied and was able to change between
various emulated NIC models successfully. I believe it would be applicable
to libvirt upstream, too.

- -Stefan

PS: Please cc: me directly on replies as I am not subscribed to this list. Thanks.


diff -Nurp libvirt.old/src/xenxs/xen_sxpr.c libvirt-0.9.8/src/xenxs/xen_sxpr.c
- --- libvirt.old/src/xenxs/xen_sxpr.c    2012-03-16 11:17:02.685042296 +0100
+++ libvirt-0.9.8/src/xenxs/xen_sxpr.c  2012-03-15 18:43:32.000000000 +0100
@@ -1873,7 +1873,9 @@ xenFormatSxprNet(virConnectPtr conn,
     }
     else {
         virBufferEscapeSexpr(buf, "(model '%s')", def->model);
- -        virBufferAddLit(buf, "(type ioemu)");
+       /* See above. Also needed when model is specified. */
+        if (xendConfigVersion <= XEND_CONFIG_MAX_VERS_NET_TYPE_IOEMU)
+            virBufferAddLit(buf, "(type ioemu)");
     }

     if (!isAttach)
diff -Nurp libvirt.old/src/xenxs/xen_xm.c libvirt-0.9.8/src/xenxs/xen_xm.c
- --- libvirt.old/src/xenxs/xen_xm.c      2012-03-16 11:17:02.645042103 +0100
+++ libvirt-0.9.8/src/xenxs/xen_xm.c    2012-03-15 18:43:32.000000000 +0100
@@ -1335,7 +1335,9 @@ static int xenFormatXMNet(virConnectPtr
     }
     else {
         virBufferAsprintf(&buf, ",model=%s", net->model);
- -        virBufferAddLit(&buf, ",type=ioemu");
+       /* See above. Also needed if model is specified. */
+        if (xendConfigVersion <= XEND_CONFIG_MAX_VERS_NET_TYPE_IOEMU)
+            virBufferAddLit(&buf, ",type=ioemu");
     }

     if (net->ifname)
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