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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?qub00jUJUs6zng9TKGjf4NT9VS50jbM97Osf/NC2ab2HsKawsnv5NjiwMXJk?= =?us-ascii?Q?tDnAHouVzc+DAe61gYJtrokxJBvHhqiKnATnj0dFsp97XFtKVKePqmHsffGm?= =?us-ascii?Q?CHpxFGCh0JNCdRhKhm0rblxUV6b7iRF1b5ANOL5K3Dv/PgJZDXYqSwA3rVZW?= =?us-ascii?Q?BZieAGbQLrO+f2Rv8MGiy0yGMrL18w3TGU2BANODNEy5erg8nPj3fHec7pUM?= =?us-ascii?Q?I2QA5cwFzozKwL7FD7tIFgduqDFgNuv73+b8ZoMLssCMvdaAXooq0EoPWM+R?= =?us-ascii?Q?E3Z2JcUrL9SobXyeGMyfu0IKcrqk9vtS8HHA9Zz93ZZ28ixVaxesu9Oqup/l?= =?us-ascii?Q?IGdSv39ib07YAmccjzZbfWb8pYKVZduRKaRuAwDwlts1Uicn6guwXVI2hPq7?= =?us-ascii?Q?LhwcQsCymhRvPoeVL8E7hvc0ZYDLFev5bY3IVfaScDkfm3iXR9s+DTrPiKwC?= =?us-ascii?Q?BIDa/lO8JNz1BJFrFo2N/Vk9WCS3TOMZp8pRIxwAI1OcCZgznXj0A/SgW7Ls?= =?us-ascii?Q?3FN6o+Wi4g9t0wX63AWnOZUApbzKdkFfFmM2f5OsSQSRYYV6pBac1PYq6EhE?= =?us-ascii?Q?IGFENI590pTzyD98LKDgZGuahWbogCvc9OfVb4nQm42/07olIVJahNQjvYBG?= =?us-ascii?Q?ho+9fBC7O4WTOpRhYl5yOREdMk+0W2HINj7J2DhXc4z4xmrnuIK4jJGZy0DK?= =?us-ascii?Q?CttfzIJVG1g2K+ItNf9+vhEnCMWqhZFMCw2t8WASZB6NwDzj7eR50eJYWIwf?= =?us-ascii?Q?KYVpGCH3YITBpLm8wmwJCoAdfpo4YmFsZZYnVcueDqZxALhD/Zp80Yq1P7N6?= =?us-ascii?Q?xI4pv5T900mbwWE3TCewdnOy21YwlasCZEZw0M64mlGDJvK0ntpncwXC6r8g?= =?us-ascii?Q?Z1DCuS9AfCFZr36ncHECk8ZsClj2o+CbSnMvhMInk6ntCw/qV07OgVAG7dGK?= =?us-ascii?Q?FWiWnnjgS1/wg92e9YgSEvQsxE/bFqyn6TpQ2JFdj88TOQGLMyI9e3GeOFan?= =?us-ascii?Q?UQa40/0V/I5lXGt/Jk41CNxDQzkdglJfNckGw7oI958381ilaGpzNTiF+OUO?= =?us-ascii?Q?76r20DcxoifXxq+yFubiNCBNFF0mc4lkAr38DT4K1uuJMdSynM131/y9V2T8?= =?us-ascii?Q?CQSKHX8tna5hUbNYuj7iIqaZ2snqyoyFO3mhv/1AI+rjciD43+pMm7HE1nNb?= =?us-ascii?Q?ZqsXDSIJj823pnvVRS0hmeqpzXN2Lb4TpQwV37mHC9ecwKta6/BjZdnaXfMs?= =?us-ascii?Q?oXfNcZEG3pgM3LVfAfPuzQJQbX304+99VFCxtQaK1CzfUznFYLXmycvqJNZi?= =?us-ascii?Q?Oy7hz85wLhQnRD8+yizuuEia?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 390adfe9-b67f-4ecd-2571-08d98fcc529b X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Oct 2021 11:09:57.4094 (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: 2I7or5PWkoOAXbQvCwn9d2OYV6LDbgP0T1XdB6c0IZEGTf2twLjWvx1PdYHFaJwK X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5080 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 15, 2021 at 01:29:16AM +0000, Tian, Kevin wrote: > Hi, Jason, > > > From: Jason Gunthorpe > > Sent: Wednesday, September 29, 2021 8:59 PM > > > > On Wed, Sep 29, 2021 at 12:38:35AM +0000, Tian, Kevin wrote: > > > > > /* If set the driver must call iommu_XX as the first action in probe() or > > > * before it attempts to do DMA > > > */ > > > bool suppress_dma_owner:1; > > > > It is not "attempts to do DMA" but more "operates the physical device > > in any away" > > > > Not having ownership means another entity could be using user space > > DMA to manipulate the device state and attack the integrity of the > > kernel's programming of the device. > > > > Does suppress_kernel_dma sounds better than suppress_dma_owner? > We found the latter causing some confusion when doing internal > code review. Somehow this flag represents "don't claim the kernel dma > ownership during driver binding". suppress_dma_owner sounds the > entire ownership is disabled... If in doubt make it suppress_iommu_whatever_the_api_is_that_isn't_called > Another thing is about DMA_OWNER_SHARED, which is set to indicate > no dma at all. Thinking more we feel that this flag is meaningless. Its > sole purpose is to show compatibility to any USER/KERNEL ownership, > and essentially the same semantics as a device which is not bound to > any driver. So we plan to remove it then pci-stub just needs one line > change to set the suppress flag. But want to check with you first in case > any oversight. It sounds reasonable, but also makes it much harder to find the few places that have this special relationship - ie we can't grep for DMA_OWNER_SHARED anymore. Jason