Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Tue, 8 Feb 2022 16:40:41 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Matthew Rosato <mjrosato@linux.ibm.com>
Cc:     Alex Williamson <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,
        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, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 24/30] vfio-pci/zdev: wire up group notifier
Message-ID: <20220208204041.GK4160@nvidia.com>
References: <20220204211536.321475-1-mjrosato@linux.ibm.com>
 <20220204211536.321475-25-mjrosato@linux.ibm.com>
 <20220208104319.4861fb22.alex.williamson@redhat.com>
 <20220208185141.GH4160@nvidia.com>
 <20220208122624.43ad52ef.alex.williamson@redhat.com>
 <438d8b1e-e149-35f1-a8c9-ed338eb97430@linux.ibm.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <438d8b1e-e149-35f1-a8c9-ed338eb97430@linux.ibm.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?vNV3KfAcmTng1uYfTJRCclhr0Ib2KYg+JpxyaxThQ5JpJE9PaO3uW5sPKe5L?=
 =?us-ascii?Q?5li/0RI/qEvtySy9oAESt+CmBG1nT9D1mEnkSGghvOvEjDxo9WITJi5mKXGt?=
 =?us-ascii?Q?AbTE7BdcuoXAUUk8peMeKJjUwsbBobkvC1YHWz270VSMPxOiAhkKUWIA+uDr?=
 =?us-ascii?Q?tvEBjatb7qrc4G2CXUer0IIE9skF4vrTZ6XHeDSEJt16rHKkNne54idkz3m7?=
 =?us-ascii?Q?RHpS0uT2IOhCJiJrYL3IStlPxyUO29uHGju2q8rrWOj2sX/qbTiInq0n/NBL?=
 =?us-ascii?Q?Oe1UaaqGMlaTklv7bCaE0bkLh9XMm+OC58eSBEl//7ZCvmqX+ypmPXgDd9BF?=
 =?us-ascii?Q?fSmk1hgdDxK7iTRBlz8a9bT6vDxzzfouqZoH5bWV3KZhBJvvSsBJ3WFTutGI?=
 =?us-ascii?Q?gAM5FpaxFi3U/8ciM1MMd3EEQZZfJGU/AO+TrjLgcDoOQ0pmzobnYDIipfMO?=
 =?us-ascii?Q?4tj0MKo++9EN7NlOycrXKyVF6mGtofusiUpj7oIler/rCcT7tx4V2e+7Z5yQ?=
 =?us-ascii?Q?BoV8iI23FU5LdkfHipK0/x/szUlNQpo9mzgfqjd/jX8K0XoXkTysFCV1Wfft?=
 =?us-ascii?Q?tiu+T+3z5W3MDwpNWzHDwFRH8sZSq8FSICkLRliHklst5ebmy+q//FbjtAT5?=
 =?us-ascii?Q?5V1CHocGQVnePsD8t12dEfOzyp098zSU6y6wreHqnNJGzHkVUQ9+3zHbu1OJ?=
 =?us-ascii?Q?/6N81wZ3ATEsihXmbdY7i8JPC14SMbl+bjeKkax0dE3ndjzfFW2e4Mv0xv7U?=
 =?us-ascii?Q?qJi1u4gFIl/MK8nBhZSd/ZLcFLY/laiI9CHTvNRv5geYcYZEFJpt7hpV67Cr?=
 =?us-ascii?Q?28naWXRzMPjUIhNKY1/HvSoGIK6uuwUGAFoT2MVZkgVo9evHAS9O5QaqLrjk?=
 =?us-ascii?Q?D95mBZMEisbjBEh5Yvs3Xu0gdtR1gKNWhIg6ts0aWJNLj9ZBE5wUylNJxQmP?=
 =?us-ascii?Q?+5wVtJkrrm//ksS796p1sRtSjK+yjkTkCYjHzoVnsLRfkf8iHkImUQxN9Fxy?=
 =?us-ascii?Q?2T4QkJBx2thNs/zrpQqSbncWCaOK45fggjz6mbK/GAfiD+yEG4QY2tPEgQkd?=
 =?us-ascii?Q?4PQCWrn08saToI1n0xgO4YDcOpqHOtnGIHnnuHRDzBw1ZMJtv9q5kfUkiIjg?=
 =?us-ascii?Q?fXfELHKlq9+j2LMJuD+bDUDrONPOh7YyqeZBQl/8aTVkw3F/zY/eQfHtFMA2?=
 =?us-ascii?Q?bFx+Fi00gcIQ5FXdvgSE7pr2ftQRpM4cOZF9Ph9RsSLmIx7uYp0K/9RjDv5P?=
 =?us-ascii?Q?FFWctQBY5QU+mCnkxAmYWuGO1tFKjxwjlbw+16KGn476OwPE82kBaY8rfu4Z?=
 =?us-ascii?Q?SOXkFj9MVte9Za+5zEPRqa2DD2IRd6Rq4q5PnxGeDk/frDksNPzDrGmQ37Lo?=
 =?us-ascii?Q?Os2+1pDDSz4OgvZtUyO1JILvEqZOFNCTYhvsTloonHKWg0+VOb1WBsftTJX6?=
 =?us-ascii?Q?AkK3o4g8tSF57LGUSdlhCndKYtpCDGfUTzpWGXxGA8QTBujoO7f6rsOYywJU?=
 =?us-ascii?Q?oe6OcKOBThdTBPC5dxTJgQYCyauk69eo7xW6R/yMdPosQe8W+xxA671u5Y1O?=
 =?us-ascii?Q?qYVj79SYibSjR5iJmXc=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 9cedd7e5-11fc-4d7e-523a-08d9eb43468d
X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Feb 2022 20:40:43.0826
 (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: 3s+Nl2uKt/2WYajHGDM/vYhHi3W7GUZ6n+csoUH0BuR2NZv9KpCUqtusqF7+x4r6
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR12MB1325
X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_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 Tue, Feb 08, 2022 at 03:33:58PM -0500, Matthew Rosato wrote:

> > Is the purpose of IOAT to associate the device to a set of KVM page
> > tables?  That seems like a container or future iommufd operation.  I
> 
> Yes, here we are establishing a relationship with the DMA table in the guest
> so that once mappings are established guest PCI operations (handled via
> special instructions in s390) don't need to go through the host but can be
> directly handled by firmware (so, effectively guest can keep running on its
> vcpu vs breaking out).

Oh, well, certainly sounds like a NAK on that - anything to do with
the DMA translation of a PCI device must go through the iommu layer,
not here.

Lets not repeat the iommu subsytem bypass mess power made please.

> It's more that non-KVM userspace doesn't care about what these ioctls are
> doing...  The enabling of 'interp, aif, ioat' is only pertinent when there
> is a KVM userspace, specifically because the information being shared /
> actions being performed as a result are only relevant to properly enabling
> zPCI features when the zPCI device is being passed through to a VM
> guest.

Then why are they KVM ioctls?

Jason