Re: [RFC] Observed lockdep circular dependency in SR-IOV paths

[Jason Gunthorpe]

On Tue, Mar 31, 2026 at 10:23:06AM -0700, Raghavendra Rao Ananta wrote:
> Hi Alex,
> 
> While running the vfio_pci_sriov_uapi_test [1] on a CONFIG_LOCKDEP
> enabled kernel (7.0-rc1), we observed the following lockdep circular
> locking dependency warning:

This loos more like a class issue, the locks used by the VF driver are
different than the locks used by the PF driver, and even though the
devsets are shared a devset should never have both the PF and VF.

Maybe shifting memory_lock into a different lock class for VFs is
enough.

However, I think it is a bad idea to hold the memory_lock while
probing a device, I'd prefer to revisit f4162eb1e2fc ("vfio/pci:
Change the PF power state to D0 before enabling VFs") and change it's
logic to rely on a private flag instead of pci_num_vf()

Then we don't need to hold the lock any longer than just setting the
flag.

Jason