From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 2573BA052E; Mon, 9 Mar 2020 10:00:34 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 515331C067; Mon, 9 Mar 2020 10:00:03 +0100 (CET) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id 3CABF23D for ; Fri, 6 Mar 2020 10:45:54 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Mar 2020 01:45:53 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,521,1574150400"; d="scan'208";a="234748382" Received: from fmsmsx103.amr.corp.intel.com ([10.18.124.201]) by orsmga008.jf.intel.com with ESMTP; 06 Mar 2020 01:45:52 -0800 Received: from fmsmsx153.amr.corp.intel.com (10.18.125.6) by FMSMSX103.amr.corp.intel.com (10.18.124.201) with Microsoft SMTP Server (TLS) id 14.3.439.0; Fri, 6 Mar 2020 01:45:43 -0800 Received: from shsmsx151.ccr.corp.intel.com (10.239.6.50) by FMSMSX153.amr.corp.intel.com (10.18.125.6) with Microsoft SMTP Server (TLS) id 14.3.439.0; Fri, 6 Mar 2020 01:45:43 -0800 Received: from shsmsx104.ccr.corp.intel.com ([169.254.5.206]) by SHSMSX151.ccr.corp.intel.com ([169.254.3.201]) with mapi id 14.03.0439.000; Fri, 6 Mar 2020 17:45:40 +0800 From: "Tian, Kevin" To: Alex Williamson CC: "kvm@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "dev@dpdk.org" , "mtosatti@redhat.com" , "thomas@monjalon.net" , "bluca@debian.org" , "jerinjacobk@gmail.com" , "Richardson, Bruce" , "cohuck@redhat.com" Thread-Topic: [PATCH v2 5/7] vfio/pci: Add sriov_configure support Thread-Index: AQHV51YaoTnickP570etlLGInd5eAKgrQJIwgA6gtQCAAWITYIAAIt7A Date: Fri, 6 Mar 2020 09:45:40 +0000 Message-ID: References: <158213716959.17090.8399427017403507114.stgit@gimli.home> <158213846731.17090.37693075723046377.stgit@gimli.home> <20200305112230.0dd77712@w520.home> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ctpclassification: CTP_NT x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiMjY4MTQ2OWItZDU1Ny00ZGViLTk5ODEtODAzYjcxMDY3OWNhIiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX05UIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE3LjEwLjE4MDQuNDkiLCJUcnVzdGVkTGFiZWxIYXNoIjoiWEFkM0paSjhCUXhKS0JQdHFpWUw0NGhCOElseFk2c1daa3dnYjdwdUVJMzJJSHlIc3Y4MGxveFhmVDFVR0VVZCJ9 dlp-product: dlpe-windows dlp-version: 11.2.0.6 dlp-reaction: no-action x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Mailman-Approved-At: Mon, 09 Mar 2020 09:59:55 +0100 Subject: Re: [dpdk-dev] [PATCH v2 5/7] vfio/pci: Add sriov_configure support X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > From: Tian, Kevin > Sent: Friday, March 6, 2020 3:57 PM >=20 > > From: Alex Williamson > > Sent: Friday, March 6, 2020 2:23 AM > > > > On Tue, 25 Feb 2020 03:08:00 +0000 > > "Tian, Kevin" wrote: > > > > > > From: Alex Williamson > > > > Sent: Thursday, February 20, 2020 2:54 AM > > > > > > > > With the VF Token interface we can now expect that a vfio userspace > > > > driver must be in collaboration with the PF driver, an unwitting > > > > userspace driver will not be able to get past the GET_DEVICE_FD ste= p > > > > in accessing the device. We can now move on to actually allowing > > > > SR-IOV to be enabled by vfio-pci on the PF. Support for this is no= t > > > > enabled by default in this commit, but it does provide a module opt= ion > > > > for this to be enabled (enable_sriov=3D1). Enabling VFs is rather > > > > straightforward, except we don't want to risk that a VF might get > > > > autoprobed and bound to other drivers, so a bus notifier is used to > > > > "capture" VFs to vfio-pci using the driver_override support. We > > > > assume any later action to bind the device to other drivers is > > > > condoned by the system admin and allow it with a log warning. > > > > > > > > vfio-pci will disable SR-IOV on a PF before releasing the device, > > > > allowing a VF driver to be assured other drivers cannot take over t= he > > > > PF and that any other userspace driver must know the shared VF toke= n. > > > > This support also does not provide a mechanism for the PF userspace > > > > driver itself to manipulate SR-IOV through the vfio API. With this > > > > patch SR-IOV can only be enabled via the host sysfs interface and t= he > > > > PF driver user cannot create or remove VFs. > > > > > > I'm not sure how many devices can be properly configured simply > > > with pci_enable_sriov. It is not unusual to require PF driver prepare > > > something before turning PCI SR-IOV capability. If you look kernel > > > PF drivers, there are only two using generic pci_sriov_configure_ > > > simple (simple wrapper like pci_enable_sriov), while most others > > > implementing their own callback. However vfio itself has no idea > > > thus I'm not sure how an user knows whether using this option can > > > actually meet his purpose. I may miss something here, possibly > > > using DPDK as an example will make it clearer. > > > > There is still the entire vfio userspace driver interface. Imagine for > > example that QEMU emulates the SR-IOV capability and makes a call out > > to libvirt (or maybe runs with privs for the PF SR-IOV sysfs attribs) > > when the guest enables SR-IOV. Can't we assume that any PF specific > > support can still be performed in the userspace/guest driver, leaving > > us with a very simple and generic sriov_configure callback in vfio-pci? >=20 > Makes sense. One concern, though, is how an user could be warned > if he inadvertently uses sysfs to enable SR-IOV on a vfio device whose > userspace driver is incapable of handling it. Note any VFIO device, > if SR-IOV capable, will allow user to do so once the module option is > turned on and the callback is registered. I felt such uncertainty can be > contained by toggling SR-IOV through a vfio api, but from your descriptio= n > obviously it is what you want to avoid. Is it due to the sequence reason, > e.g. that SR-IOV must be enabled before userspace PF driver sets the > token? >=20 reading again I found that you specifically mentioned "the PF driver user=20 cannot create or remove VFs.". However I failed to get the rationale=20 behind. If the VF drivers have built the trust with the PF driver through the token, what is the problem of allowing the PF driver to further manage= =20 SR-IOV itself? suppose any VF removal will be done in a cooperate way to avoid surprise impact to related VF drivers. then possibly a new vfio ioctl for setting the VF numbers plus a token from the userspace driver could also serve the purpose of this patch series (GET_DEVICE_FD + sysfs)? Thanks Kevin