On Sun, May 14, 2023 at 04:39:36PM -0400, Michael S. Tsirkin wrote: > On Sun, May 14, 2023 at 12:24:32PM -0700, syzbot wrote: > > syzbot has bisected this issue to: > > > > commit a3c06ae158dd6fa8336157c31d9234689d068d02 > > Author: Parav Pandit <parav@xxxxxxxxxx> > > Date: Tue Jan 5 10:32:03 2021 +0000 > > > > vdpa_sim_net: Add support for user supported devices > > > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > > I don't see how this can be related, I don't think the test setup uses > vdpa sim at all. Yeah, it's totally bogus. You can see it by looking at the bisection log[1]. [1] https://syzkaller.appspot.com/text?tag=Log&x=16e372c6280000 The initial bisection logs make it clear that it is *trivially* easy to reproduce, and that the failure signature is: crashed: possible deadlock in {ext4_xattr_set_handle,ext4_setattr,ext4_xattr_set_handle} However, somewhere in the bisection, we start seeing this: run #0: boot failed: WARNING in kvm_wait run #1: boot failed: WARNING in kvm_wait run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK This is a completely different failure signature, and the "WARNING in kvm_wait" should be ignored, and this should be considered a "git bisect good". However, the syzkaller bisection doesn't understand this, and so it gets sent down the primrose path. :-( Unfortunately, there isn't a good way to tell the syzkaller bisection, "go home, your drunk", and to tell it to try again, perhaps with a human-supplied discriminator of what should be considered a valid failure signature. In the ideal world, a human should be able to give it a setup set of bisection "good" and "bad" commits, along with a regexp for what a failure should look like, and perhaps with a hint of how many tries it should use before assuming that a bisection result is "good", and to teach it to assume that the bisection has "bad" after seeing a single failure signature. If the above is too much to ask, in the slightly-less-ideal world, there would be a way to give "#syz test" a count argument, so we could have syzkaller try N times, for when we need to do a manual bisection using "#syz test".... - Ted
