Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 16 May 2022 20:05:52 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Matthew Rosato <mjrosato@linux.ibm.com>
Cc:     alex.williamson@redhat.com, linux-s390@vger.kernel.org,
        cohuck@redhat.com, schnelle@linux.ibm.com, farman@linux.ibm.com,
        pmorel@linux.ibm.com, borntraeger@linux.ibm.com, hca@linux.ibm.com,
        gor@linux.ibm.com, gerald.schaefer@linux.ibm.com,
        agordeev@linux.ibm.com, svens@linux.ibm.com, frankja@linux.ibm.com,
        david@redhat.com, imbrenda@linux.ibm.com, vneethv@linux.ibm.com,
        oberpar@linux.ibm.com, freude@linux.ibm.com, thuth@redhat.com,
        pasic@linux.ibm.com, pbonzini@redhat.com, corbet@lwn.net,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH v7 17/22] vfio-pci/zdev: add open/close device hooks
Message-ID: <20220516230552.GO1343366@nvidia.com>
References: <20220513191509.272897-1-mjrosato@linux.ibm.com>
 <20220513191509.272897-18-mjrosato@linux.ibm.com>
 <20220516172734.GE1343366@nvidia.com>
 <7a31ec36-ceaf-dcef-8bd0-2b4732050aed@linux.ibm.com>
 <20220516183558.GN1343366@nvidia.com>
 <305208c4-db8a-5751-2ffc-753751a70815@linux.ibm.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <305208c4-db8a-5751-2ffc-753751a70815@linux.ibm.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Mjn9ITNW/AHZMfRQkogHi7By/C6NGHNzKFv5HFQVm4VzPp0TkKMUfoGYu0kR?=
 =?us-ascii?Q?xZaDKfvq3aVZ7kvdKrangap9a1v/iK9nbO3Lv6W+e3mGBbrC90wK8PlYeLIm?=
 =?us-ascii?Q?YQzret62omCu2n61N+3gk+H8ve2BEK9BJzxdJO/adh+eKHfgygnv1tFqgxOy?=
 =?us-ascii?Q?ddRM2+I5n2DM8DAPyFdfinYrEuEObglmgDaYSV908qtF5w8lNHkmU7qmyVkl?=
 =?us-ascii?Q?N9MJvUGrcRHlVcb21P5XcsnTQ7y6Ds4oYIAsNiI8jDKSvOdGUduMhPgOUd+Y?=
 =?us-ascii?Q?xfJgJTk/yrSSg321VAx80QCcpzlsTob7jKcb2hgoVqWSHPXLyztvlpL4uN/3?=
 =?us-ascii?Q?8s76a7EtvHY7hzmPqoaVDJ8n2+TdatmwXD+3pSckY0ePgmYpxw7JN4++oia/?=
 =?us-ascii?Q?VbEDqhvxJGf1VM2HLeKFVDgl/yszjIq9Iy5jVvtzAU9+B/r/TgPA5oGXOo2A?=
 =?us-ascii?Q?HdgdVeYhUhPtn3Gd5EAwLTLXsPgarTPtzWB5qpAibWXn5X/qaXXdPJV720lO?=
 =?us-ascii?Q?MhtAdcbT2e0KdU/D8bn/DfnCPgTSBypdWcXjurjfUPV31v5I4rFEe5/6P3Cd?=
 =?us-ascii?Q?+F10bYjjHX8Q+m4NySPWCe4VXji4QE2CYaLcn6mhXjp4zgOrQ8PDFZiyGtqy?=
 =?us-ascii?Q?4oNekKVBYobHbAKohh7KTuvwa9Fro7UGzP5K+G7AziBEDs1zABBORU/w9/Js?=
 =?us-ascii?Q?oh/wzJiYrhXkznd0dmrh0avyPjMIXFMLlefVzm2zIBbFHTzMcpd1s6m0KdSQ?=
 =?us-ascii?Q?3Ffo3GhD9dPTwG9//pbA8jq/+xBgXVi15vi+b6Q1qgq+HXlkOWEOqiwynlR8?=
 =?us-ascii?Q?Eld8ryHKwo6dxzHuOauAO2CP0oN+mn6O77KBDCEjWrM9s8TCcQ5vV5krq5V+?=
 =?us-ascii?Q?DYBborA/laQoXqGPAVOLso9AMraGxe80Ro3bVn/U2BSCx9h/aXQyJmtLxRwL?=
 =?us-ascii?Q?a+YW4o/gpWR8hKUyHjUxc0kt6x75eLcyj5y2CKhaotVigMp9fhwp6f3HXUE6?=
 =?us-ascii?Q?q5VwsGJ1ZtIrUN1tzgkt2RY7x8o/FP6FRWGwC+BrfDiQzqQW59gm6Nf0csx+?=
 =?us-ascii?Q?NtP/3JzEETZbauVPrt7jHK0bVm6+/7UTLKeIGfpzsQWeW+reywKwHR3ufHlW?=
 =?us-ascii?Q?X4wz8Ef6RwHa4jV7HS4rDx6cYf+a8Na0nj5z72IxaiSnFHRqEQ1LWyBsaqJk?=
 =?us-ascii?Q?crrJxe2dkeCBhKTxj/wIQcgoDYrPZCiEExVKehm0gZaoPoDP61v3eJKNkWdy?=
 =?us-ascii?Q?RkY4I7as2PR6cPYkQZsKUCc1YqpHqy+JcekswjKyoK7Rg4cd+So/+WFUilwP?=
 =?us-ascii?Q?7dsM5424625k7WsxSA9EEBJ2JWGEkqBZZ4jcJ114XNOkVygAyIOJlm7CDrEL?=
 =?us-ascii?Q?ygTjtGYhmYYpumu08r0SEob6MFsZ7nUkuXHgvEwo9mUnoDCcMvlpmddyaDq+?=
 =?us-ascii?Q?6Qy+JR7ci7PQFmczGHuElc/HO/lkgfq2ZIu48XFf6DEc6CNRbIppspJi/gd4?=
 =?us-ascii?Q?Ifg4YIlBsLe5XY/FDanD/UxhIcMhemjJKvWXKVDABb3CwJTykZIa29/kQBFw?=
 =?us-ascii?Q?eUzY+5MSymwPzTP4AmkJxPacWjI5PFe+c6TM2UHwPdiItbxK39gm6hpSOVmu?=
 =?us-ascii?Q?d5BaYzeAhvhJx7GtjjznX209KoQSYkgp/loSNCkgkBd5U0rhScgjhuD+Ud/N?=
 =?us-ascii?Q?YKvNxqOWcOujgo4bHmEg30a23MJf9LAHuJ3iJ0yHElP1LQNYgmRwGTo8oQAX?=
 =?us-ascii?Q?WobbV0FOwQ=3D=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 5a5f7bff-8da2-4358-c8c2-08da3790a0ab
X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 May 2022 23:05:53.7870
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: eEkH9STYkZ0yzxAVvDjL/wLzoZYa36OXmVaPeMPB4K1/ZMDSxQi0vJD8rhce12GR
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB5782
X-Spam-Status: No, score=-1.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,
        RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, May 16, 2022 at 05:59:01PM -0400, Matthew Rosato wrote:
> On 5/16/22 2:35 PM, Jason Gunthorpe wrote:
> > On Mon, May 16, 2022 at 02:30:46PM -0400, Matthew Rosato wrote:
> > 
> > > Conceptually I think this would work for QEMU anyway (it always sets the kvm
> > > before we open the device).  I tried to test the idea quickly but couldn't
> > > get the following to apply on vfio-next or your vfio_group_locking -- but I
> > > understand what you're trying to do so I'll re-work and try it out.
> > 
> > I created it on 8c9350e9bf43de1ebab3cc8a80703671e6495ab4 which is the
> > vfio_group_locking.. I can send you a github if it helps
> > https://github.com/jgunthorpe/linux/commits/vfio_group_lockin
> > 
> Thanks -- I was able to successfully test your proposed idea (+ some changes
> to make it compile :)) on top of vfio_group_locking along with a modified
> version of my zdev series.  I also tried it out with vfio-ap successfully,
> but have nothing to test GVT with.
> 
> That said, this has caused me to realize that 'iommu:
> iommu_group_claim_dma_owner() must always assign a domain' breaks s390x
> vfio-pci :( I wonder if it is due to the way s390x PCI currently switches
> between dma ops and iommu ops.  It looks like it breaks vfio-ap mdevs too,
> but I know less about that --  I will have to investigate both more
> tomorrow.

At the very least it appears that s390 thinks that attach/detach_dev
are strictly paired and that isn't how the iommu ops are defined.

attach_dev can be called multiple times without any detach_dev.

Possibly the unbalance of zpci_register_ioat / zpci_unregister_ioat
causes the trouble?

Jason