FAILED: Patch "PCI/IOV: Fix race between SR-IOV enable/disable and hotplug" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From a5338e365c4559d7b4d7356116b0eb95b12e08d5 Mon Sep 17 00:00:00 2001
From: Niklas Schnelle <[email protected]>
Date: Tue, 16 Dec 2025 23:14:03 +0100
Subject: [PATCH] PCI/IOV: Fix race between SR-IOV enable/disable and hotplug

Commit 05703271c3cd ("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.

---
 drivers/pci/iov.c | 4 ++++
 1 file changed, 4 insertions(+)

index 7de5b18647beb..4a659c34935e1 100644
@@ -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;
 

2.51.0