Debugging issues that span both libkrun and the guest kernel (e.g. a virtio driver bug or a TSI networking regression) requires iterating on changes in both repos and re-running the failing test. Without this option, libkrunfw must be manually built and installed into the right prefix each time before running the libkrun test. With LIBKRUNFW_SRC= pointing at a libkrunfw source tree, a single command rebuilds both libkrun and libkrunfw from their current dirty state, installs them into test-prefix/, and runs the test. The same command can be re-run as either repo is edited: make -j11 test TEST=net-passt LIBKRUNFW_SRC=~/src/libkrunfw The sub-make inherits the parent's jobserver for parallelism. A warning is emitted when test-prefix contains a custom libkrunfw from a previous LIBKRUNFW_SRC= run, so the user knows tests are not using the system libkrunfw. Assisted-by: OpenCode:claude-opus-4.6 Signed-off-by: Matej Hrica <mhrica@redhat.com>