Re: [PATCH V3 01/14] blk-mq: add blk_mq_max_nr_hw_queues()

On Thu, Aug 10, 2023 at 08:09:27AM +0800, Ming Lei wrote:

1) some archs support 'nr_cpus=1' for kdump kernel, which is fine, since
num_possible_cpus becomes 1.

2) some archs do not support 'nr_cpus=1', and have to rely on
'max_cpus=1', so num_possible_cpus isn't changed, and kernel just boots
with single online cpu. That causes trouble because blk-mq limits single
queue.

And we need to fix case 2.  We need to drop the is_kdump support, and
if they want to force less cpus they need to make nr_cpus=1 work.