I saw vm's check several times, I think since this test is about "blkiotune", a vm is needed, so before testing we can check if we can get the vm, if vm is None, I think we should raise a error.TestError.Do you agree with me?
And I have an idea, we can define get_blkio_parameter() and set_blkio_parameter() in run_virsh_blkiotune(), so if vm's check passed, the vm will be global variables, no need to get it again in the two function(other params too), what do you think?