[PATCH V2 5/9] scsi: hisi: take blk_mq_max_nr_hw_queues() into account for calculating io vectors

[Ming Lei]

On Thu, Jul 27, 2023 at 08:35:06AM +0100, John Garry wrote:
> On 27/07/2023 02:15, Ming Lei wrote:
> > > > hisi_sas_v3_hw.c
> > > > +++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
> > > > @@ -2550,6 +2550,9 @@ static int interrupt_preinit_v3_hw(struct hisi_hba *hisi_hba)
> > > >    	hisi_hba->cq_nvecs = vectors - BASE_VECTORS_V3_HW - hisi_hba->iopoll_q_cnt;
> > > > +	if (hisi_hba->cq_nvecs > scsi_max_nr_hw_queues())
> > > > +		hisi_hba->cq_nvecs = scsi_max_nr_hw_queues();
> > > > +
> > > >    	shost->nr_hw_queues = hisi_hba->cq_nvecs + hisi_hba->iopoll_q_cnt;
> > > For other drivers you limit the max MSI vectors which we try to allocate
> > > according to scsi_max_nr_hw_queues(), but here you continue to alloc the
> > > same max vectors but then limit the driver's completion queue count. Why not
> > > limit the max MSI vectors also here?
> 
> Ah, checking again, I think that this driver always allocates maximum
> possible MSI due to arm interrupt controller driver bug - see comment at top
> of function interrupt_preinit_v3_hw(). IIRC, there was a problem if we
> remove and re-insert the device driver that the GIC ITS fails to allocate
> MSI unless all MSI were previously allocated.

My question is actually why hisi_hba->iopoll_q_cnt is subtracted from
allocated vectors since io poll queues does _not_ use msi vector.

So it isn't related with driver's msi vector allocation bug, is it?



Thanks,
Ming