You set a timeout of 30 seconds, but your initramfs takes 31 seconds to load a firmware package. Solution: Use dynamic timeouts. 4.0 supports adaptive_timeout: true which learns from the last 5 successful boots.
A developer changes kernel config or QEMU arguments. QEMU Boot Tester 4.0 boots the image, detects that virtio-blk initialization now takes 2 seconds longer and throws a new mmc0: error -110 , and flags the change as a regression before any manual test is done. qemu boot tester 4.0