linux-kernel - Re: [PATCH 0/2] PCI/IOV: Add missing PCI rescan-remove locking when enabling/disabling SR-IOV

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Message-ID: <20250926210223.GA2267349@bhelgaas>
Date: Fri, 26 Sep 2025 16:02:23 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Lukas Wunner <lukas@...ner.de>, Keith Busch <kbusch@...nel.org>,
	Gerd Bayer <gbayer@...ux.ibm.com>,
	Matthew Rosato <mjrosato@...ux.ibm.com>,
	Benjamin Block <bblock@...ux.ibm.com>,
	Halil Pasic <pasic@...ux.ibm.com>, Farhan Ali <alifm@...ux.ibm.com>,
	Julian Ruess <julianr@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] PCI/IOV: Add missing PCI rescan-remove locking when
 enabling/disabling SR-IOV

On Tue, Aug 26, 2025 at 10:52:07AM +0200, Niklas Schnelle wrote:
> Hi Bjorn, Hi Lukas,
> 
> This series fixes missing PCI rescan-remove locking in sriov_disable()
> and sriov_enable() the former of which was observed to cause a double
> remove / list corruption on s390. The first patch is the fix itself and
> gives more details while the second patch is an optional proposal to add
> a lockdep assertion to pci_stop_and_remove_bus_device() to catch missing
> rescan-remove locking more easily in the future. If applied without the
> first patch disabling SR-IOV via "echo 0 > /sys/bus/pci/devices/<dev>
> /sriov_numvfs" triggers the lockdep assertion. I haven't found an easy
> way to trigger the assertion in the sriov_enable() case but I checked
> callers.
> 
> Also since the sriov_add_vfs() path is not excercised on s390 due to
> pdev->no_vf_scan I did some basic testing on an x86 test system with an
> SR-IOV capable ConnectX-6 DX NIC.
> 
> Thanks,
> Niklas
> 
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
> Niklas Schnelle (2):
>       PCI/IOV: Add missing PCI rescan-remove locking when enabling/disabling SR-IOV
>       PCI: Add lockdep assertion in pci_stop_and_remove_bus_device()
> 
>  drivers/pci/iov.c    | 5 +++++
>  drivers/pci/pci.h    | 2 ++
>  drivers/pci/probe.c  | 2 +-
>  drivers/pci/remove.c | 1 +
>  4 files changed, 9 insertions(+), 1 deletion(-)

Applied to pci/virtualization, hoping to squeeze into v6.18.