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PCI/IOV: Fix race between SR-IOV enable/disable and hotplug

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Commit 05703271c3 ("PCI/IOV: Add PCI rescan-remove locking when
enabling/disabling SR-IOV") tried to fix a race between the VF removal
inside sriov_del_vfs() and concurrent hot unplug by taking the PCI
rescan/remove lock in sriov_del_vfs(). Similarly the PCI rescan/remove lock
was also taken in sriov_add_vfs() to protect addition of VFs.

This approach however causes deadlock on trying to remove PFs with SR-IOV
enabled because PFs disable SR-IOV during removal and this removal happens
under the PCI rescan/remove lock. So the original fix had to be reverted.

Instead of taking the PCI rescan/remove lock in sriov_add_vfs() and
sriov_del_vfs(), fix the race that occurs with SR-IOV enable and disable vs
hotplug higher up in the callchain by taking the lock in
sriov_numvfs_store() before calling into the driver's sriov_configure()
callback.

Fixes: 05703271c3 ("PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV")
Reported-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Gerd Bayer <gbayer@linux.ibm.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251216-revert_sriov_lock-v3-2-dac4925a7621@linux.ibm.com
This commit is contained in:
Niklas Schnelle 2025-12-16 23:14:03 +01:00 committed by Bjorn Helgaas
parent 2fa119c0e5
commit a5338e365c
1 changed files with 4 additions and 0 deletions
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4
drivers/pci/iov.c
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@ -495,7 +495,9 @@ static ssize_t sriov_numvfs_store(struct device *dev,
if (num_vfs == 0) {
/* disable VFs */
pci_lock_rescan_remove();
ret = pdev->driver->sriov_configure(pdev, 0);
pci_unlock_rescan_remove();
goto exit;
}
@ -507,7 +509,9 @@ static ssize_t sriov_numvfs_store(struct device *dev,
goto exit;
}
pci_lock_rescan_remove();
ret = pdev->driver->sriov_configure(pdev, num_vfs);
pci_unlock_rescan_remove();
if (ret < 0)
goto exit;