[PATCH 6.18 647/752] Revert "PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV"

Sasha Levin
2026-02-28T17:57:42Z

From: Niklas Schnelle <schnelle@linux.ibm.com>

[ Upstream commit 2fa119c0e5e528453ebae9e70740e8d2d8c0ed5a ]

This reverts commit 05703271c3cd ("PCI/IOV: Add PCI rescan-remove locking
when enabling/disabling SR-IOV"), which causes a deadlock by recursively
taking pci_rescan_remove_lock when sriov_del_vfs() is called as part of
pci_stop_and_remove_bus_device(). For example with the following sequence
of commands:

$ echo <NUM> > /sys/bus/pci/devices/<pf>/sriov_numvfs
$ echo 1 > /sys/bus/pci/devices/<pf>/remove

A trimmed trace of the deadlock on a mlx5 device is as below:

zsh/5715 is trying to acquire lock:
000002597926ef50 (pci_rescan_remove_lock){+.+.}-{3:3}, at: sriov_disable+0x34/0x140

but task is already holding lock:
000002597926ef50 (pci_rescan_remove_lock){+.+.}-{3:3}, at: pci_stop_and_remove_bus_device_locked+0x24/0x80
...
Call Trace:
[<00000259778c4f90>] dump_stack_lvl+0xc0/0x110
[<00000259779c844e>] print_deadlock_bug+0x31e/0x330
[<00000259779c1908>] __lock_acquire+0x16c8/0x32f0
[<00000259779bffac>] lock_acquire+0x14c/0x350
[<00000259789643a6>] __mutex_lock_common+0xe6/0x1520
[<000002597896413c>] mutex_lock_nested+0x3c/0x50
[<00000259784a07e4>] sriov_disable+0x34/0x140
[<00000258f7d6dd80>] mlx5_sriov_disable+0x50/0x80 [mlx5_core]
[<00000258f7d5745e>] remove_one+0x5e/0xf0 [mlx5_core]
[<00000259784857fc>] pci_device_remove+0x3c/0xa0
[<000002597851012e>] device_release_driver_internal+0x18e/0x280
[<000002597847ae22>] pci_stop_bus_device+0x82/0xa0
[<000002597847afce>] pci_stop_and_remove_bus_device_locked+0x5e/0x80
[<00000259784972c2>] remove_store+0x72/0x90
[<0000025977e6661a>] kernfs_fop_write_iter+0x15a/0x200
[<0000025977d7241c>] vfs_write+0x24c/0x300
[<0000025977d72696>] ksys_write+0x86/0x110
[<000002597895b61c>] __do_syscall+0x14c/0x400
[<000002597896e0ee>] system_call+0x6e/0x90

This alone is not a complete fix as it restores the issue the cited commit
tried to solve. A new fix will be provided as a follow on.

Fixes: 05703271c3cd ("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>
Acked-by: Gerd Bayer <gbayer@linux.ibm.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251216-revert_sriov_lock-v3-1-dac4925a7621@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/iov.c | 5 -----
1 file changed, 5 deletions(-)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 77dee43b78583..ac4375954c947 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -629,18 +629,15 @@ static int sriov_add_vfs(struct pci_dev *dev, u16 num_vfs)
if (dev->no_vf_scan)
return 0;

- pci_lock_rescan_remove();
for (i = 0; i < num_vfs; i++) {
rc = pci_iov_add_virtfn(dev, i);
if (rc)
goto failed;
}
- pci_unlock_rescan_remove();
return 0;
failed:
while (i--)
pci_iov_remove_virtfn(dev, i);
- pci_unlock_rescan_remove();

return rc;
}
@@ -765,10 +762,8 @@ static void sriov_del_vfs(struct pci_dev *dev)
struct pci_sriov *iov = dev->sriov;
int i;

- pci_lock_rescan_remove();
for (i = 0; i < iov->num_VFs; i++)
pci_iov_remove_virtfn(dev, i);
- pci_unlock_rescan_remove();
}

static void sriov_disable(struct pci_dev *dev)
--
2.51.0