Re: [PATCH v5 2/4] s390/pci: Preserve FMB state in device re-enablement

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but there is a missing resource cleanup in `zpci_reenable_device()` on the `zpci_set_irq()` error path. If `zpci_set_irq()` fails, the function returns immediately without calling `zpci_disable_device()`, unlike the subsequent IOMMU registration error path. This leaves the device enabled in an inconsistent state.
--

commit 94bfdcea02e7e7dca9c322a0dc40fac61a9fb275
Author: Omar Elghoul <oelghoul@linux.ibm.com>

s390/pci: Preserve FMB state in device re-enablement

This commit introduces zpci_fmb_reenable_device() to check the FMB state and
ensure it is enabled. It resets the counters and handles re-enabling if the
FMB was already active.

> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
> index 2910d4038d39c..1eb6aa772eb3f 100644
> --- a/arch/s390/pci/pci.c
> +++ b/arch/s390/pci/pci.c
[ ... ]
> @@ -737,9 +765,13 @@ int zpci_reenable_device(struct zpci_dev *zdev)
>  	}
>  
>  	rc = zpci_iommu_register_ioat(zdev, &status);
> -	if (rc)
> +	if (rc) {
>  		zpci_disable_device(zdev);
> +		return rc;
> +	}

[Severity: High]
This isn't a bug introduced by this patch, but there is a pre-existing issue
with resource cleanup in zpci_reenable_device().

If zpci_set_irq() fails earlier in this function:

        if (zdev->msi_nr_irqs > 0) {
                rc = zpci_set_irq(zdev);
                if (rc)
                        return rc;
        }

It returns immediately without calling zpci_disable_device(), unlike the
subsequent zpci_iommu_register_ioat() error path. Does this leave the device
enabled in the firmware but failed in Linux, rendering it unusable and
leaking its enabled state?

>  
> +	guard(mutex)(&zdev->fmb_lock);
> +	zpci_fmb_reenable_device(zdev);
>  	return rc;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260626175525.37370-1-oelghoul@linux.ibm.com?part=2