Re: [PATCH 1/5] scsi: hisi_sas: Add host_tagset_enable module param for v3 hw

[John Garry]

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@xxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxx/
>
> And, Niklas tried to help fix this problem: https://lore.kernel.org/ 
> linux-scsi/ZynmfyDA9R-lrW71@ryzen/
>
> 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

And pm8001 driver will have the same issue, so we need to find a proper fix.

Let me consider this issue more.