runqemu greps the image for certain magic strings (root=/dev/sd, root=/dev/hd) to determine which disk interface (ide, scsi, virtio) it should use for booting. This is noticeably slow for me (laptop, big image) and even fails when the machine is loaded: grep: memory exhausted Aborted It then falls back to virtio, which works for me. Besides the performance, the check is also unreliable, because those strings might be contained in images for other reasons. We should have an explicit mechanism for images to configure this aspect. This can end up in .qemuboot.conf, and then the grep commands can be removed.
Merged into master: http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=f57393b386499c607e01ce1b3f1503b2cdca73d9