From: Jason Gunthorpe <jgg@ziepe.ca>
To: Raghavendra Rao Ananta <rananta@google.com>
Cc: Alex Williamson <alex@shazbot.org>,
David Matlack <dmatlack@google.com>,
Vipin Sharma <vipinsh@google.com>,
Josh Hilke <jrhilke@google.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [RFC] Observed lockdep circular dependency in SR-IOV paths
Date: Mon, 6 Apr 2026 19:34:28 -0300 [thread overview]
Message-ID: <20260406223428.GK2551565@ziepe.ca> (raw)
In-Reply-To: <CAJHc60zTBn9xMksi-_UBK=W07rp2vGVZ9ToYhFyadNz4zCVHAA@mail.gmail.com>
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
next prev parent reply other threads:[~2026-04-06 22:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-31 17:23 [RFC] Observed lockdep circular dependency in SR-IOV paths Raghavendra Rao Ananta
2026-04-06 22:34 ` Jason Gunthorpe [this message]
2026-04-07 3:59 ` Alex Williamson
2026-04-08 15:46 ` Raghavendra Rao Ananta
2026-04-10 16:43 ` Alex Williamson
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