linux-kernel - Re: [PATCH 1/5] scsi: hisi_sas: Add host_tagset

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Message-ID: <34a6208e-2802-8e3f-1a4d-92919407e7a8@huawei.com>
Date: Tue, 1 Apr 2025 09:12:30 +0800
From: yangxingui <yangxingui@...wei.com>
To: John Garry <john.g.garry@...cle.com>, Yihang Li <liyihang9@...wei.com>,
	<martin.petersen@...cle.com>, <James.Bottomley@...senPartnership.com>
CC: <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linuxarm@...wei.com>, <liuyonglong@...wei.com>, <prime.zeng@...ilicon.com>,
	<linux-ide@...r.kernel.org>
Subject: Re: [PATCH 1/5] scsi: hisi_sas: Add host_tagset_enable module param
 for v3 hw

On 2025/3/31 15:43, John Garry wrote:
> On 29/03/2025 09:49, yangxingui wrote:
>> Hi，John
>>
>> On 2025/3/29 16:50, John Garry wrote:
>>> On 29/03/2025 07:32, Yihang Li wrote:
>>>
>>> +
>>>
>>>> From: Xingui Yang<yangxingui@...wei.com>
>>>>
>>>> After driver exposes all HW queues and application submits IO to 
>>>> multiple
>>>> queues in parallel, if NCQ and non-NCQ commands are mixed to sata disk,
>>>> ata_qc_defer() causes non-NCQ commands to be requeued and possibly 
>>>> repeated
>>>> forever.
>>>
>>> I don't think that it is a good idea to mask out bugs with module 
>>> parameters.
>>>
>>> Was this the same libata/libsas issue reported some time ago?
>>
>> Yeah，related to this issue: https://lore.kernel.org/linux-block/ 
>> eef1e927-c9b2-c61d-7f48-92e65d8b0418@...wei.com/
>>
>> And, Niklas tried to help fix this problem: https://lore.kernel.org/ 
>> linux-scsi/ZynmfyDA9R-lrW71@...en/
>>
>> Considering that there is no formal solution yet. And our users rarely 
>> use SATA disks and SAS disks together on a single machine. For this 
>> reason, they can flexibly turn off the exposure of multiple queues in 
>> the scenario of using only SATA disks. In addition, it is also 
>> convenient to conduct performance comparison tests to expose multiple 
>> hardware queues and single queues.
>>
> 
> The change in this series does not even solve the issues, as:
> - you do not guarantee no SAS/SATA mix without that module param enabled
> - the driver still uses managed interrupts in both cases, so with 
> disabling host_tagset you are now exposed to CPU hotplug issue of IO 
> being in-flight when HW queue interrupt is shutdown

Yes, there will be such problems.

> 
> And pm8001 driver will have the same issue, so we need to find a proper 
> fix.
> 
> Let me consider this issue more.

OK.

Thanks,
Xingui