Re: [PATCH] scsi: aacraid: Stop using PCI_IRQ_AFFINITY

[John Meneghini <jmeneghi@redhat.com>]

OK John. Thanks for the patch.

We will test this out on our test bed here at Red Hat and let you know if this solves the problem.

/John

On 7/15/25 7:15 AM, John Garry wrote:
> When PCI_IRQ_AFFINITY is set for calling pci_alloc_irq_vectors(), it
> means interrupts are spread around the available CPUs. It also means that
> the interrupts become managed, which means that an interrupt is shutdown
> when all the CPUs in the interrupt affinity mask go offline.
> 
> Using managed interrupts in this way means that we should ensure that
> completions should not occur on HW queues where the associated interrupt
> is shutdown. This is typically achieved by ensuring only CPUs which are
> online can generate IO completion traffic to the HW queue which they are
> mapped to (so that they can also serve completion interrupts for that
> HW queue).
> 
> The problem in the driver is that a CPU can generate completions to
> a HW queue whose interrupt may be shutdown, as the CPUs in the HW queue
> interrupt affinity mask may be offline. This can cause IOs to never
> complete and hang the system. The driver maintains its own CPU <-> HW
> queue mapping for submissions, see aac_fib_vector_assign(), but this
> does not reflect the CPU <-> HW queue interrupt affinity mapping.
> 
> Commit 9dc704dcc09e ("scsi: aacraid: Reply queue mapping to CPUs based on
> IRQ affinity") tried to remedy this issue may mapping CPUs properly to
> HW queue interrupts. However this was later reverted in commit c5becf57dd56
> ("Revert "scsi: aacraid: Reply queue mapping to CPUs based on IRQ
> affinity") - it seems that there were other reports of hangs. I guess that
> this was due to some implementation issue in the original commit or
> maybe a HW issue.
> 
> Fix the very original hang by just not using managed interrupts by not
> setting PCI_IRQ_AFFINITY.  In this way, all CPUs will be in each HW
> queue affinity mask, so should not create completion problems if any
> CPUs go offline.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
> build tested only
> 
> diff --git a/drivers/scsi/aacraid/comminit.c b/drivers/scsi/aacraid/comminit.c
> index 28cf18955a08..726c8531b7d3 100644
> --- a/drivers/scsi/aacraid/comminit.c
> +++ b/drivers/scsi/aacraid/comminit.c
> @@ -481,8 +481,7 @@ void aac_define_int_mode(struct aac_dev *dev)
>   	    pci_find_capability(dev->pdev, PCI_CAP_ID_MSIX)) {
>   		min_msix = 2;
>   		i = pci_alloc_irq_vectors(dev->pdev,
> -					  min_msix, msi_count,
> -					  PCI_IRQ_MSIX | PCI_IRQ_AFFINITY);
> +					  min_msix, msi_count, PCI_IRQ_MSIX);
>   		if (i > 0) {
>   			dev->msi_enabled = 1;
>   			msi_count = i;