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Date:   Mon, 10 Jul 2023 08:41:09 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Wen Xiong <wenxiong@linux.ibm.com>,
        Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH 2/2] nvme-pci: use blk_mq_max_nr_hw_queues() to
 calculate io queues
Message-ID: <20230710064109.GB24519@lst.de>
References: <20230708020259.1343736-1-ming.lei@redhat.com> <20230708020259.1343736-3-ming.lei@redhat.com>
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On Sat, Jul 08, 2023 at 10:02:59AM +0800, Ming Lei wrote:
> Take blk-mq's knowledge into account for calculating io queues.
> 
> Fix wrong queue mapping in case of kdump kernel.
> 
> On arm and ppc64, 'maxcpus=1' is passed to kdump command line, see
> `Documentation/admin-guide/kdump/kdump.rst`, so num_possible_cpus()
> still returns all CPUs.

That's simply broken.  Please fix the arch code to make sure
it does not return a bogus num_possible_cpus value for these
setups, otherwise you'll have to paper over it in all kind of
drivers.