On Tue, 24 Jan 2017, Roger Pau Monné wrote: > Hello, > > The following commit: > > commit 3a6c9172ac5951e6dac2b3f6cbce3cfccdec5894 > Author: Juergen Gross <jgr...@suse.com> > Date: Tue Nov 22 07:10:58 2016 +0100 > > xen: create qdev for each backend device > > Prevents me from running QEMU on FreeBSD/Xen, the following is printed on the > QEMU log: > > char device redirected to /dev/pts/2 (label serial0) > xen be core: xen be core: can't open gnttab device > can't open gnttab device > xen be core: xen be core: can't open gnttab device > can't open gnttab device > > # xl create -c ~/domain.cfg > Parsing config from /root/domain.cfg > libxl: error: libxl_dm.c:2201:device_model_spawn_outcome: Domain 32:domain 32 > device model: spawn failed (rc=-3) > libxl: error: libxl_create.c:1506:domcreate_devmodel_started: Domain > 32:device model did not start: -3 > libxl: error: libxl_dm.c:2315:kill_device_model: Device Model already exited > libxl: error: libxl.c:1572:libxl__destroy_domid: Domain 32:Non-existant domain > libxl: error: libxl.c:1531:domain_destroy_callback: Domain 32:Unable to > destroy guest > libxl: error: libxl.c:1458:domain_destroy_cb: Domain 32:Destruction of domain > failed > # cat /var/log/xen/qemu-dm-domain.log > char device redirected to /dev/pts/2 (label serial0) > xen be core: xen be core: can't open gnttab device > can't open gnttab device > xen be core: xen be core: can't open gnttab device > can't open gnttab device > > I'm not really familiar with any of that code, but I think that using > qdev_init_nofail is wrong, since on FreeBSD/Xen for example we don't yet > support the gnttab device, so initialization of the Xen Qdisk backend can fail > (and possibly the same applies to Linux if someone decides to compile a kernel > without the gnttab device). Yet QEMU can be used without the Qdisk backend.
How did you manage to configure QEMU before? The configure script had xc_gnttab_open calls in it up to Xen 4.6. I am happy to support a use case where the kernel doesn't have gntdev, but it needs to be explicit: we need to detect it in the configure script, then avoid the initialization of devices which require it.
