Re: [patch V5 4/8] nvme-pci: Simplify interrupt allocation

[Thomas Gleixner]

On Fri, 15 Feb 2019, Ming Lei wrote:
> > +    * If only one interrupt is available, combine write and read
> > +    * queues. If 'write_queues' is set, ensure it leaves room for at
> > +    * least one read queue.
> > +    */
> > +   if (nrirqs == 1)
> > +           nr_read_queues = 0;
> > +   else if (write_queues >= nrirqs)
> > +           nr_read_queues = nrirqs - 1;
> > +   else
> > +           nr_read_queues = nrirqs - write_queues;
> > +
> > +   dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues;
> > +   affd->set_size[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues;
> > +   dev->io_queues[HCTX_TYPE_READ] = nr_read_queues;
> > +   affd->set_size[HCTX_TYPE_READ] = nr_read_queues;
> > +   affd->nr_sets = nr_read_queues ? 2 : 1;
> >  }
> 
> .calc_sets is called only if more than .pre_vectors is available,
> then dev->io_queues[HCTX_TYPE_DEFAULT] may not be set in case of
> (nvecs == affd->pre_vectors + affd->post_vectors).

Hmm, good catch. The delta patch below should fix that, but I have to go
through all the possible cases in pci_alloc_irq_vectors_affinity() once
more with brain awake.

Thanks,

        tglx

8<---------------------

--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2092,6 +2092,10 @@ static int nvme_setup_irqs(struct nvme_d
        }
        dev->io_queues[HCTX_TYPE_POLL] = this_p_queues;
 
+       /* Initialize for the single interrupt case */
+       dev->io_queues[HCTX_TYPE_DEFAULT] = 1;
+       dev->io_queues[HCTX_TYPE_READ] = 0;
+
        return pci_alloc_irq_vectors_affinity(pdev, 1, irq_queues,
                              PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
 }