kernel/drivers/pci/iov.c, branch linux-5.10.y

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

2026-03-04T12:20:21Z

[ Upstream commit a5338e365c4559d7b4d7356116b0eb95b12e08d5 ] 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. Fixes: 05703271c3cd ("PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV") Reported-by: Benjamin Block Signed-off-by: Niklas Schnelle Signed-off-by: Bjorn Helgaas Reviewed-by: Benjamin Block Reviewed-by: Gerd Bayer Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20251216-revert_sriov_lock-v3-2-dac4925a7621@linux.ibm.com Signed-off-by: Sasha Levin

Revert "PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV"

2026-03-04T12:20:21Z

[ 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 > /sys/bus/pci/devices//sriov_numvfs $ echo 1 > /sys/bus/pci/devices//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 Signed-off-by: Niklas Schnelle Signed-off-by: Bjorn Helgaas Reviewed-by: Benjamin Block Acked-by: Gerd Bayer 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

PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV

2025-10-29T13:01:12Z

commit 05703271c3cdcc0f2a8cf6ebdc45892b8ca83520 upstream. Before disabling SR-IOV via config space accesses to the parent PF, sriov_disable() first removes the PCI devices representing the VFs. Since commit 9d16947b7583 ("PCI: Add global pci_lock_rescan_remove()") such removal operations are serialized against concurrent remove and rescan using the pci_rescan_remove_lock. No such locking was ever added in sriov_disable() however. In particular when commit 18f9e9d150fc ("PCI/IOV: Factor out sriov_add_vfs()") factored out the PCI device removal into sriov_del_vfs() there was still no locking around the pci_iov_remove_virtfn() calls. On s390 the lack of serialization in sriov_disable() may cause double remove and list corruption with the below (amended) trace being observed: PSW: 0704c00180000000 0000000c914e4b38 (klist_put+56) GPRS: 000003800313fb48 0000000000000000 0000000100000001 0000000000000001 00000000f9b520a8 0000000000000000 0000000000002fbd 00000000f4cc9480 0000000000000001 0000000000000000 0000000000000000 0000000180692828 00000000818e8000 000003800313fe2c 000003800313fb20 000003800313fad8 #0 [3800313fb20] device_del at c9158ad5c #1 [3800313fb88] pci_remove_bus_device at c915105ba #2 [3800313fbd0] pci_iov_remove_virtfn at c9152f198 #3 [3800313fc28] zpci_iov_remove_virtfn at c90fb67c0 #4 [3800313fc60] zpci_bus_remove_device at c90fb6104 #5 [3800313fca0] __zpci_event_availability at c90fb3dca #6 [3800313fd08] chsc_process_sei_nt0 at c918fe4a2 #7 [3800313fd60] crw_collect_info at c91905822 #8 [3800313fe10] kthread at c90feb390 #9 [3800313fe68] __ret_from_fork at c90f6aa64 #10 [3800313fe98] ret_from_fork at c9194f3f2. This is because in addition to sriov_disable() removing the VFs, the platform also generates hot-unplug events for the VFs. This being the reverse operation to the hotplug events generated by sriov_enable() and handled via pdev->no_vf_scan. And while the event processing takes pci_rescan_remove_lock and checks whether the struct pci_dev still exists, the lack of synchronization makes this checking racy. Other races may also be possible of course though given that this lack of locking persisted so long observable races seem very rare. Even on s390 the list corruption was only observed with certain devices since the platform events are only triggered by config accesses after the removal, so as long as the removal finished synchronously they would not race. Either way the locking is missing so fix this by adding it to the sriov_del_vfs() helper. Just like PCI rescan-remove, locking is also missing in sriov_add_vfs() including for the error case where pci_stop_and_remove_bus_device() is called without the PCI rescan-remove lock being held. Even in the non-error case, adding new PCI devices and buses should be serialized via the PCI rescan-remove lock. Add the necessary locking. Fixes: 18f9e9d150fc ("PCI/IOV: Factor out sriov_add_vfs()") Signed-off-by: Niklas Schnelle Signed-off-by: Bjorn Helgaas Reviewed-by: Benjamin Block Reviewed-by: Farhan Ali Reviewed-by: Julian Ruess Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20250826-pci_fix_sriov_disable-v1-1-2d0bc938f2a3@linux.ibm.com Signed-off-by: Greg Kroah-Hartman

PCI/IOV: Mark VFs as not implementing PCI_COMMAND_MEMORY

2020-09-21T20:42:11Z

For VFs, the Memory Space Enable bit in the Command Register is hard-wired to 0. Add a new bit to signify devices where the Command Register Memory Space Enable bit does not control the device's response to MMIO accesses. Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory") Signed-off-by: Matthew Rosato Acked-by: Bjorn Helgaas Signed-off-by: Alex Williamson

s390/pci: create links between PFs and VFs

2020-05-20T08:22:51Z

On s390 PCI Virtual Functions (VFs) are scanned by firmware and are made available to Linux via the hot-plug interface. As such the common code path of doing the scan directly using the parent Physical Function (PF) is not used and fenced off with the no_vf_scan attribute. Even if the partition created the VFs itself e.g. using the sriov_numvfs attribute of a PF, the PF/VF links thus need to be established after the fact. To do this when a VF is plugged we scan through all functions on the same zbus and test whether they are the parent PF in which case we establish the necessary links. With these links established there is now no more need to fence off pci_iov_remove_virtfn() for pdev->no_vf_scan as the common code now works fine. Signed-off-by: Niklas Schnelle Acked-by: Bjorn Helgaas Reviewed-by: Pierre Morel Link: https://lore.kernel.org/r/20200506154139.90609-3-schnelle@linux.ibm.com Signed-off-by: Vasily Gorbik

PCI/IOV: Introduce pci_iov_sysfs_link() function

2020-05-20T08:22:50Z

Currently pci_iov_add_virtfn() scans the SR-IOV BARs, adds the VF to the bus and also creates the sysfs links between the newly added VF and its parent PF. With pdev->no_vf_scan fencing off the entire pci_iov_add_virtfn() call s390 as the sole pdev->no_vf_scan user thus ends up missing these sysfs links which are required for example by QEMU/libvirt. Instead of duplicating the code refactor pci_iov_add_virtfn() to make sysfs link creation callable separately. Signed-off-by: Niklas Schnelle Acked-by: Bjorn Helgaas Reviewed-by: Pierre Morel Link: https://lore.kernel.org/r/20200506154139.90609-1-schnelle@linux.ibm.com Signed-off-by: Vasily Gorbik

PCI/IOV: Fix memory leak in pci_iov_add_virtfn()

2019-12-09T21:51:32Z

In the implementation of pci_iov_add_virtfn() the allocated virtfn is leaked if pci_setup_device() fails. The error handling is not calling pci_stop_and_remove_bus_device(). Change the goto label to failed2. Fixes: 156c55325d30 ("PCI: Check for pci_setup_device() failure in pci_iov_add_virtfn()") Link: https://lore.kernel.org/r/20191125195255.23740-1-navid.emamdoost@gmail.com Signed-off-by: Navid Emamdoost Signed-off-by: Bjorn Helgaas

Merge branch 'pci/trivial'

2019-11-28T14:54:55Z

- Fix typos and comments (Bjorn Helgaas) - Fix Kconfig whitespace errors (Krzysztof Kozlowski) * pci/trivial: PCI: Fix indentation PCI: Fix typos PCI: Remove useless comments and tidy others PCI: Remove unnecessary includes # Conflicts: # drivers/pci/probe.c

PCI: Remove unnecessary includes

2019-10-17T20:18:44Z

Remove unnecessary includes. Signed-off-by: Bjorn Helgaas

PCI/IOV: Serialize sysfs sriov_numvfs reads vs writes

2019-10-15T21:39:12Z

When sriov_numvfs is being updated, we call the driver->sriov_configure() function, which may enable VFs and call probe functions, which may make new devices visible. This all happens before before sriov_numvfs_store() updates sriov->num_VFs, so previously, concurrent sysfs reads of sriov_numvfs returned stale values. Serialize the sysfs read vs the write so the read returns the correct num_VFs value. [bhelgaas: hold device_lock instead of checking mutex_is_locked()] Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991 Link: https://lore.kernel.org/r/20190911072736.32091-1-pierre.cregut@orange.com Signed-off-by: Pierre Crégut Signed-off-by: Bjorn Helgaas