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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8b3ef6fbc50sm19588776d6.10.2026.04.29.05.38.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2026 05:38:34 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wI4BV-0000000HLk7-2n9U; Wed, 29 Apr 2026 09:38:33 -0300 Date: Wed, 29 Apr 2026 09:38:33 -0300 From: Jason Gunthorpe To: mboone@akamai.com Cc: Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Mark Bloch , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] net/mlx5: check whether VFs are assigned before disabling SR-IOV Message-ID: <20260429123833.GM849557@ziepe.ca> References: <20260428-mlx5-sriov-in-use-check-v1-1-c7b9e18c99a8@akamai.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260428-mlx5-sriov-in-use-check-v1-1-c7b9e18c99a8@akamai.com> On Tue, Apr 28, 2026 at 08:04:14PM +0200, Max Boone via B4 Relay wrote: > From: Max Boone > > When MLX5 cards are passed through to a VM, disabling SR-IOV by > setting the sriov_numvfs to 0 will render the machine unstable. What? How does that happen? > -void mlx5_sriov_disable(struct pci_dev *pdev, bool num_vf_change) > +int mlx5_sriov_disable(struct pci_dev *pdev, bool num_vf_change) > { > struct mlx5_core_dev *dev = pci_get_drvdata(pdev); > struct devlink *devlink = priv_to_devlink(dev); > int num_vfs = pci_num_vf(dev->pdev); > > + if (pci_vfs_assigned(dev->pdev)) { > + mlx5_core_warn(dev, "can't disable sriov, VFs are assigned\n"); > + return -EPERM; > + } *barf* WTF did this come from? Grep says only Xen makes this true, so this is all working around some Xen brokenness in their "assignment" ? If people care about Xen pci_is_dev_assigned() should be be purged and pciback should be fixed to not "make the machine unstable" when it is removed during a VF teardown. Or at the very least this nasty Xen intrustion should be placed in the PCI core code and removed from the drivers. Also, no, you can't fail mlx5_sriov_disable() it is called during driver remove and cannot fail in that flow. Jason