Currently, the vhost-user-test is not correct. When in qtest mode, the accel is qtest, not kvm. So when the client side of vhost-user-test send 'VHOST_USER_SET_VRING_CALL' msg, the 'fd' will no be added in 'fds' in 'vhost_set_vring_file'. In 'chr_read' of the server side in the vhost-user-test, it calls 'qemu_chr_fe_get_msgfds' to get the fd in 'VHOST_USER_SET_VRING_CALL'. Though there is no fd returned, but as the 'fd' is not initialized so 'fd' maybe valid, and 'qemu_set_nonblock' will be success. Even worse, 'qemu_set_nonblock' doesn't check the return value of fcntl.
So this cause the interesting bug here: there are three issues, but they combined and will bypass the qtest. This patchset tries to address these issue. Li Qiang (3): tests: vhost-user-test: initialize 'fd' in chr_read vhost-user: add fds inf 'vhost_set_vring_file' in qtest util: check the return value of fcntl in qemu_set_{block, nonblock} hw/virtio/vhost-user.c | 3 ++- tests/vhost-user-test.c | 2 +- util/oslib-posix.c | 8 ++++++-- 3 files changed, 9 insertions(+), 4 deletions(-) -- 2.17.1