Re: [PATCH v3 05/10] s390/pci: Restore IRQ unconditionally for the zPCI device

Niklas Schnelle
2025-09-15T08:39:12Z

On Thu, 2025-09-11 at 11:33 -0700, Farhan Ali wrote:
> Commit c1e18c17bda6 ("s390/pci: add zpci_set_irq()/zpci_clear_irq()"),
> introduced the zpci_set_irq() and zpci_clear_irq(), to be used while
> resetting a zPCI device.
>
> Commit da995d538d3a ("s390/pci: implement reset_slot for hotplug slot"),
> mentions zpci_clear_irq() being called in the path for zpci_hot_reset_device().
> But that is not the case anymore and these functions are not called
> outside of this file.

If you're doing another version I think you could add a bit more
information on why this still works for existing recovery based on my
investigation in
https://lore.kernel.org/lkml/052ebdbb6f2d38025ca4345ee51e4857e19bb0e4.camel@linux.ibm.com/

Even if you don't add more explanations, I'd tend to just drop the
above paragraph as it doesn't seem relevant and sounds like
zpci_hot_reset_device() doesn't clear IRQs. As explained in the linked
mail there really is no need to call zpci_clear_irq() in
zpci_hot_reset_device() as the CLP disable does disable IRQs. It's
really only the state tracking that can get screwed up but is also fine
for drivers which end up doing the tear down.

>
> However after a CLP disable/enable reset, the device's IRQ are
> unregistered, but the flag zdev->irq_registered does not get cleared. It
> creates an inconsistent state and so arch_restore_msi_irqs() doesn't
> correctly restore the device's IRQ. This becomes a problem when a PCI
> driver tries to restore the state of the device through
> pci_restore_state(). Restore IRQ unconditionally for the device and remove
> the irq_registered flag as its redundant.

s/its/it's/

>
> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
> ---
> arch/s390/include/asm/pci.h | 1 -
> arch/s390/pci/pci_irq.c | 9 +--------
> 2 files changed, 1 insertion(+), 9 deletions(-)
>
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 41f900f693d9..aed19a1aa9d7 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -145,7 +145,6 @@ struct zpci_dev {
> u8 has_resources : 1;
> u8 is_physfn : 1;
> u8 util_str_avail : 1;
> - u8 irqs_registered : 1;
> u8 tid_avail : 1;
> u8 rtr_avail : 1; /* Relaxed translation allowed */
> unsigned int devfn; /* DEVFN part of the RID*/
> diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
> index 84482a921332..e73be96ce5fe 100644
> --- a/arch/s390/pci/pci_irq.c
> +++ b/arch/s390/pci/pci_irq.c
> @@ -107,9 +107,6 @@ static int zpci_set_irq(struct zpci_dev *zdev)
> else
> rc = zpci_set_airq(zdev);
>
> - if (!rc)
> - zdev->irqs_registered = 1;
> -
> return rc;
> }
>
> @@ -123,9 +120,6 @@ static int zpci_clear_irq(struct zpci_dev *zdev)
> else
> rc = zpci_clear_airq(zdev);
>
> - if (!rc)
> - zdev->irqs_registered = 0;
> -
> return rc;
> }
>
> @@ -427,8 +421,7 @@ bool arch_restore_msi_irqs(struct pci_dev *pdev)
> {
> struct zpci_dev *zdev = to_zpci(pdev);
>
> - if (!zdev->irqs_registered)
> - zpci_set_irq(zdev);
> + zpci_set_irq(zdev);
> return true;
> }
>

Code looks good to me. With or without my suggestions for the commit
message:

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>