On Wed, 2025-11-19 at 13:34 +0100, Niklas Schnelle wrote:
> Hi Bjorn,
>
> Doing additional testing for a distribution backport of commit
> 05703271c3cd ("PCI/IOV: Add PCI rescan-remove locking when
> enabling/disabling SR-IOV") Benjamin found a hang with s390's
> recover attribute. Further investigation showed this to be a deadlock by
> recursively trying to take pci_rescan_remove lock when removing a PF
> with enabled SR-IOV.
>
> The issue can be reproduced on both s390 and x86_64 with:
>
> $ echo <NUM> > /sys/bus/pci/devices/<pf>/sriov_numvfs
> $ echo 1 > /sys/bus/pci/devices/<pf>/remove
>
> As this seems worse than the original, hard to hit, race fixed by the
> cited commit I think we first want to revert the broken fix.
>
> Following that patch 2 attempts to fix the original issue by taking the
> PCI rescan/remove lock directly before calling into the driver's
> sriov_configure() callback enforcing the rule that this should only
> be called with the pci_rescan_remove_lock held.
>
> Thanks,
> Niklas
>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
> Changes in v2:
> - Collected R-b from Benjamin
> - Link to v1: https://lore.kernel.org/r/20251030-revert_sriov_lock-v1-0-70f82ade426f@linux.ibm.com
>
> ---
> Niklas Schnelle (2):
> Revert "PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV"
> PCI/IOV: Fix race between SR-IOV enable/disable and hotplug
>
> drivers/pci/iov.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
> ---
> base-commit: dcb6fa37fd7bc9c3d2b066329b0d27dedf8becaa
> change-id: 20251029-revert_sriov_lock-aef4557f360f
>
> Best regards,
Since this is really a regression without a separate report, yet this
has a description and reproducer I'm just adding this here:
#regzbot ^introduced: 05703271c3cd