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Tue, 15 Jun 2021 14:59:02 -0700 (PDT) Received: from redhat.com ([198.99.80.109]) by smtp.gmail.com with ESMTPSA id v14sm58471ote.15.2021.06.15.14.59.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Jun 2021 14:59:01 -0700 (PDT) Date: Tue, 15 Jun 2021 15:59:00 -0600 From: Alex Williamson To: Jason Gunthorpe Cc: Max Gurtovoy , cohuck@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aviadye@nvidia.com, oren@nvidia.com, shahafs@nvidia.com, parav@nvidia.com, artemp@nvidia.com, kwankhede@nvidia.com, ACurrid@nvidia.com, cjia@nvidia.com, yishaih@nvidia.com, kevin.tian@intel.com, hch@infradead.org, targupta@nvidia.com, shameerali.kolothum.thodi@huawei.com, liulongfang@huawei.com, yan.y.zhao@intel.com Subject: Re: [PATCH 09/11] PCI: add matching checks for driver_override binding Message-ID: <20210615155900.51f09c15.alex.williamson@redhat.com> In-Reply-To: <20210615204216.GY1002214@nvidia.com> References: <20210603160809.15845-10-mgurtovoy@nvidia.com> <20210608152643.2d3400c1.alex.williamson@redhat.com> <20210608224517.GQ1002214@nvidia.com> <20210608192711.4956cda2.alex.williamson@redhat.com> <117a5e68-d16e-c146-6d37-fcbfe49cb4f8@nvidia.com> <20210614124250.0d32537c.alex.williamson@redhat.com> <70a1b23f-764d-8b3e-91a4-bf5d67ac9f1f@nvidia.com> <20210615090029.41849d7a.alex.williamson@redhat.com> <20210615150458.GR1002214@nvidia.com> <20210615102049.71a3c125.alex.williamson@redhat.com> <20210615204216.GY1002214@nvidia.com> Organization: Red Hat X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 15 Jun 2021 17:42:16 -0300 Jason Gunthorpe wrote: > On Tue, Jun 15, 2021 at 10:20:49AM -0600, Alex Williamson wrote: > > On Tue, 15 Jun 2021 12:04:58 -0300 > > Jason Gunthorpe wrote: > > > > > On Tue, Jun 15, 2021 at 09:00:29AM -0600, Alex Williamson wrote: > > > > > > > "vfio" override in PCI-core plays out for other override types. Also I > > > > don't think dynamic IDs should be handled uniquely, new_id_store() > > > > should gain support for flags and userspace should be able to add new > > > > dynamic ID with override-only matches to the table. Thanks, > > > > > > Why? Once all the enforcement is stripped out the only purpose of the > > > new flag is to signal a different prepration of modules.alias - which > > > won't happen for the new_id path anyhow > > > > Because new_id allows the admin to insert a new pci_device_id which has > > been extended to include a flags field and intentionally handling > > dynamic IDs differently from static IDs seems like generally a bad > > thing. > > I'd agree with you if there was a functional difference at runtime, > but since that was all removed, I don't think we should touch new_id. > > This ends up effectively being only a kbuild related patch that > changes how modules.alias is built. But it wasn't all removed. The proposal had: a) Short circuit the dynamic ID match b) Fail a driver-override-only match without a driver_override c) Fail a non-driver-override-only match with a driver_override Max is only proposing removing c). b) alone is a functional, runtime difference. As per my previous example, think about using it as effectively an anti-match. Userspace can create dynamic entries that will be matched before static entries that can demote a driver to not be able to bind to a device automatically. That's functional and useful, I can't think of any other way we have to effectively remove a static match entry from a driver. Thanks, Alex