Comment 164 for bug 1470250

I also see a few virtio changes between -34 and -35:

4c56763 virtio-scsi: fix various bad behavior on aborted requests
2a821e5 virtio-scsi: avoid cancelling uninitialized work items
3c50c21 block: virtio_blk: don't hold spin lock during world switch

I'm going to perform a full bisect against all changes to be sure we find the correct commit that caused this. In parallel, I'll build and test a kernel with those prior 3 commits reverted as a quick test.