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[159.2.73.22]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8d6339bc438sm600898385a.26.2026.04.06.15.34.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Apr 2026 15:34:29 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1w9sWa-0000000E5Cx-1DNj; Mon, 06 Apr 2026 19:34:28 -0300 Date: Mon, 6 Apr 2026 19:34:28 -0300 From: Jason Gunthorpe To: Raghavendra Rao Ananta Cc: Alex Williamson , David Matlack , Vipin Sharma , Josh Hilke , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC] Observed lockdep circular dependency in SR-IOV paths Message-ID: <20260406223428.GK2551565@ziepe.ca> References: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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