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Subject: Re: [PATCH] nvme: determine the number of IO queues
To:     Aaron Ma <aaron.ma@canonical.com>,
        Maxim Levitsky <mlevitsk@redhat.com>,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
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From:   Minwoo Im <minwoo.im.dev@gmail.com>
Message-ID: <fbc19fb1-5e2e-ff39-5295-f38195fb8d7c@gmail.com>
Date:   Thu, 18 Apr 2019 22:33:35 +0900
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On 4/18/19 9:52 PM, Aaron Ma wrote:
> 
> 
> On 4/18/19 8:13 PM, Minwoo Im wrote:
>>> Yes the IO queues number is 0's based, but driver would return error and
>>> remove the nvme device as dead.
>>
>> IMHO, if a controller indicates an error with this set_feature command,
>> then
>> we need to figure out why the controller was returning the error to host.
>>
>> If you really want to use at least a single queue to see an alive I/O
>> queue,
>> controller should not return the error because as you mentioned above,
>> NCQA, NSQA will be returned as 0-based.  If an error is there, that could
>> mean that controller may not able to provide even a single queue for I/O.
> 
> I was thinking about try to set 1 I/O queue in driver to try to probe
> NVME device.
> If it works, at least system can bootup to debug instead of just remove
> NVME device and kernel boot hang at loading rootfs.

If the controller returns error for that command, how can we assure that
the controller would support a single I/O queue ?

> 
> If you still concern this 1 I/O queue I can still set it as
> *count = 0;
> 
> At least we try all count, NVME device still failed to respond.
> 
> Regards,
> Aaron
> 
>>
>> Thanks,
>> Minwoo Im