where is the irq effective affinity set from pci_alloc_irq_vectors_affinity()?

[Olivier Langlois <olivier@trillion01.com>]

I am trying to understand the result that the nvme driver has when it
calls pci_alloc_irq_vectors_affinity() from nvme_setup_irqs()
(drivers/nvme/host/pci.c)

$ cat /proc/interrupts | grep nvme
 63:          9          0          0          0  PCI-MSIX-0000:00:04.0
0-edge      nvme0q0
 64:          0          0          0     237894  PCI-MSIX-0000:00:04.0
1-edge      nvme0q1

$ cat /proc/irq/64/smp_affinity_list
0-3

$ cat /proc/irq/64/effective_affinity_list 
3

I think that this happens somewhere below pci_msi_setup_msi_irqs()
(drivers/pci/msi/irqdomain.c)
but I am losing track of what is done precisely because I am not sure
of what is the irq_domain on my system.

I have experimented by playing with the nvme io queues num that is
passed to pci_msi_setup_msi_irqs()
as the max_vectors params.

The set irq effective affinity appears to always be the last cpu of the
affinity mask.

I would like to have some control on the selected effective_affinity as
I am trying to use NOHZ_FULL effectively on my system.

NOTE:
I am NOT using irqbalance

thank you,