From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDD96C4320E for ; Fri, 13 Aug 2021 17:45:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B75CE6103A for ; Fri, 13 Aug 2021 17:45:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229535AbhHMRp3 (ORCPT ); Fri, 13 Aug 2021 13:45:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:42290 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229607AbhHMRp2 (ORCPT ); Fri, 13 Aug 2021 13:45:28 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 07E1760F51; Fri, 13 Aug 2021 17:45:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628876701; bh=bjNRxrk7zkv1bWv18PnoYS0DrsVT6mJBjm94a5siq1s=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=rVmzHkHhe2OWZsF033BKoxTswdFF/eMUxnledbjriHTbCZkWlAHm9HKyLbtF/H1Cl 5xAQ4w23l1qAcwRIO/lGPTnqceoufh08fatkyeUNJ/YQT+MAMUx417ihiIgBfQba3O 46gIsPG+vzTsNLCzqq3NdtDyRER2IZa3sBStd0D9D6bf2r7hqOaotOmu1h1cyqoZbo 5FvEqlpzAR/5EpbuMtsti5xd61YF8HowfVNesn4K/dvpGHf35B36dAwk/iyJCtJqny qaLXUKXRQ6u9D9wOKrd8si+ZekC/V/+wBHZFdv4oVAN+RWgdVdtIg7ldyegIMifCSv wSVZ2aCkUBgRw== Date: Fri, 13 Aug 2021 12:44:59 -0500 From: Bjorn Helgaas To: Max Gurtovoy Cc: Jason Gunthorpe , Yishai Hadas , bhelgaas@google.com, corbet@lwn.net, alex.williamson@redhat.com, diana.craciun@oss.nxp.com, kwankhede@nvidia.com, eric.auger@redhat.com, masahiroy@kernel.org, michal.lkml@markovi.net, linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kbuild@vger.kernel.org, maorg@nvidia.com, leonro@nvidia.com Subject: Re: [PATCH 09/12] PCI: Add a PCI_ID_F_VFIO_DRIVER_OVERRIDE flag to struct pci_device_id Message-ID: <20210813174459.GA2594783@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <580beaa0-d15d-4e42-5a7b-073885416df9@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Aug 13, 2021 at 02:21:41AM +0300, Max Gurtovoy wrote: > > On 8/12/2021 11:26 PM, Bjorn Helgaas wrote: > > On Thu, Aug 12, 2021 at 04:51:26PM -0300, Jason Gunthorpe wrote: > > > On Thu, Aug 12, 2021 at 10:57:07AM -0500, Bjorn Helgaas wrote: > > > > On Thu, Aug 12, 2021 at 10:27:28AM -0300, Jason Gunthorpe wrote: > > > > > On Wed, Aug 11, 2021 at 02:07:37PM -0500, Bjorn Helgaas wrote: > > > > > > On Thu, Aug 05, 2021 at 09:23:57PM -0300, Jason Gunthorpe wrote: > > > > > > Do the other bus types have a flag analogous to > > > > > > PCI_ID_F_VFIO_DRIVER_OVERRIDE? If we're doing something similar to > > > > > > other bus types, it'd be nice if the approach were similar. > > > > > They could, this series doesn't attempt it. I expect the approach to > > > > > be similar as driver_override was copied from PCI to other > > > > > busses. When this is completed I hope to take a look at it. > > > > I think this would make more sense as two patches: > > > > > > > > - Add a "PCI_ID_DRIVER_OVERRIDE" flag. This is not VFIO-specific, > > > > since nothing in PCI depends on the VFIO-ness of drivers that use > > > > the flag. The only point here is that driver id_table entries > > > > with this flag only match when driver_override matches the driver. > > > This would require using two flags, one to indicate the above to the > > > PCI code and another to indicate the vfio_pci string to > > > file2alias. This doesn't seem justified at this point, IMHO. > > I don't think it requires two flags. do_pci_entry() has: > > > > if (flags & PCI_ID_F_VFIO_DRIVER_OVERRIDE) > > strcpy(alias, "vfio_pci:"); > > > > I'm just proposing a rename: > > > > s/PCI_ID_F_VFIO_DRIVER_OVERRIDE/PCI_ID_DRIVER_OVERRIDE/ > > > > > > - Update file2alias.c to export the flags and the "vfio_pci:" alias. > > > > This seems to be the only place where VFIO comes into play, and > > > > putting it in a separate patch will make it much smaller and it > > > > will be clear how it could be extended for other buses. > > > Well, I don't want to see a flag called PCI_ID_DRIVER_OVERRIDE mapped > > > to the string "vfio_pci", that is just really confusing. > > Hahaha, I see, that's fair :) It confused me for a long time why you > > wanted "VFIO" in the flag name because from the kernel's point of > > view, the flag is not related to any VFIO-ness. It's only related to > > a special variety of driver_override, and VFIO happens to be one user > > of it. > > In my original patch I used > > #define PCI_ID_DRIVER_OVERRIDE PCI_ID_F_VFIO_DRIVER_OVERRIDE > > and in the pci core code I used PCI_ID_DRIVER_OVERRIDE in the "if" clause. > > So we can maybe do that and leave the option to future update of the define > without changing the core code. > > In the future we can have something like: > > #define PCI_ID_DRIVER_OVERRIDE (PCI_ID_F_VFIO_DRIVER_OVERRIDE | > PCI_ID_F_MY_BUS_DRIVER_OVERRIDE) > > The file2alias.c still have to use the exact PCI_ID_F_VFIO_DRIVER_OVERRIDE > flag to add "vfio_" prefix. > > Is that better ? I don't think it's worth having two separate #defines. If we need more in the future, we can add them when we need them. What if we renamed "flags" to be specifically for this override case, e.g., "override_only"? Then the flag could be PCI_ID_F_VFIO_DRIVER_OVERRIDE, which would trigger a "vfio_" prefix in file2alias.c, but pci_match_device() could just check for it being non-zero, without caring whether the reason is VFIO or something else, e.g., pci_match_device(...) { ... if (found_id->override_only) { if (dev->driver_override) return found_id; ... Bjorn