On Sat, 25 Jul 2020 08:40:07 +0800 Jason Wang <jasow...@redhat.com> wrote:
> On 2020/7/24 下午11:34, Cornelia Huck wrote: > > On Fri, 24 Jul 2020 11:17:57 -0400 > > "Michael S. Tsirkin"<m...@redhat.com> wrote: > > > >> On Fri, Jul 24, 2020 at 04:56:27PM +0200, Cornelia Huck wrote: > >>> On Fri, 24 Jul 2020 09:30:58 -0400 > >>> "Michael S. Tsirkin"<m...@redhat.com> wrote: > >>> > >>>> On Fri, Jul 24, 2020 at 03:27:18PM +0200, Cornelia Huck wrote: > >>>>> When I start qemu with a second virtio-net-ccw device (i.e. adding > >>>>> -device virtio-net-ccw in addition to the autogenerated device), I get > >>>>> a segfault. gdb points to > >>>>> > >>>>> #0 0x000055d6ab52681d in virtio_net_get_config (vdev=<optimized out>, > >>>>> config=0x55d6ad9e3f80 "RT") at > >>>>> /home/cohuck/git/qemu/hw/net/virtio-net.c:146 > >>>>> 146 if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { > >>>>> > >>>>> (backtrace doesn't go further) > >>> The core was incomplete, but running under gdb directly shows that it > >>> is just a bog-standard config space access (first for that device). > >>> > >>> The cause of the crash is that nc->peer is not set... no idea how that > >>> can happen, not that familiar with that part of QEMU. (Should the code > >>> check, or is that really something that should not happen?) > >>> > >>> What I don't understand is why it is set correctly for the first, > >>> autogenerated virtio-net-ccw device, but not for the second one, and > >>> why virtio-net-pci doesn't show these problems. The only difference > >>> between -ccw and -pci that comes to my mind here is that config space > >>> accesses for ccw are done via an asynchronous operation, so timing > >>> might be different. > >> Hopefully Jason has an idea. Could you post a full command line > >> please? Do you need a working guest to trigger this? Does this trigger > >> on an x86 host? > > Yes, it does trigger with tcg-on-x86 as well. I've been using > > > > s390x-softmmu/qemu-system-s390x -M s390-ccw-virtio,accel=tcg -cpu > > qemu,zpci=on > > -m 1024 -nographic -device virtio-scsi-ccw,id=scsi0,devno=fe.0.0001 > > -drive file=/path/to/image,format=qcow2,if=none,id=drive-scsi0-0-0-0 > > -device > > scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1 > > -device virtio-net-ccw > > > > It seems it needs the guest actually doing something with the nics; I > > cannot reproduce the crash if I use the old advent calendar moon buggy > > image and just add a virtio-net-ccw device. > > > > (I don't think it's a problem with my local build, as I see the problem > > both on my laptop and on an LPAR.) > > > It looks to me we forget the check the existence of peer. > > Please try the attached patch to see if it works. Thanks, that patch gets my guest up and running again. So, FWIW, Tested-by: Cornelia Huck <coh...@redhat.com> Any idea why this did not hit with virtio-net-pci (or the autogenerated virtio-net-ccw device)?