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Tue, 26 Apr 2022 13:53:47 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::ec2d:9167:1b47:2db2]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::ec2d:9167:1b47:2db2%6]) with mapi id 15.20.5186.021; Tue, 26 Apr 2022 13:53:47 +0000 Date: Tue, 26 Apr 2022 10:53:45 -0300 From: Jason Gunthorpe To: Yi Liu Cc: "Tian, Kevin" , "Peng, Chao P" , "Sun, Yi Y" , "qemu-devel@nongnu.org" , "david@gibson.dropbear.id.au" , "thuth@redhat.com" , "farman@linux.ibm.com" , "mjrosato@linux.ibm.com" , "akrowiak@linux.ibm.com" , "pasic@linux.ibm.com" , "jjherne@linux.ibm.com" , "jasowang@redhat.com" , "kvm@vger.kernel.org" , "nicolinc@nvidia.com" , "eric.auger@redhat.com" , "eric.auger.pro@gmail.com" , "peterx@redhat.com" Subject: Re: [RFC 15/18] vfio/iommufd: Implement iommufd backend Message-ID: <20220426135345.GN2125828@nvidia.com> References: <20220414104710.28534-1-yi.l.liu@intel.com> <20220414104710.28534-16-yi.l.liu@intel.com> <20220422145815.GK2120790@nvidia.com> <3576770b-e4c2-cf11-da0c-821c55ab9902@intel.com> Content-Type: text/plain; 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envelope-from=jgg@nvidia.com; helo=NAM02-BN1-obe.outbound.protection.outlook.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Apr 26, 2022 at 05:55:29PM +0800, Yi Liu wrote: > > I also suggest falling back to using "/dev/char/%u:%u" if the above > > does not exist which prevents "vfio/devices/vfio" from turning into > > ABI. > > do you mean there is no matched file under /dev/vfio/devices/? Is this > possible? The layout of /dev/ depens on udev rules, so it is possible. I only suggested it to avoid creating ABI here. > > It would be a good idea to make a general open_cdev function that does > > all this work once the sysfs is found and cdev read out of it, all the > > other vfio places can use it too. > > hmmm, it's good to have a general open_cdev() function. But I guess this > is the only place in VFIO to open the device cdev. Do you mean the vdpa > stuffes? Any place that starts from a sysfs name would be interested - I don't know what vdpa does Jason