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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?gQgPbuFH0i3eBDxdu6iS3HGixpdalBoPVB25FDcIW6Vviv4Ymr7dk3ZBELfK?= =?us-ascii?Q?jpYa3pyH1H0iNA8OkpxlgMCqhPc6DDGApeLj41UKmMFmHCx2hGRG+mYaKX8u?= =?us-ascii?Q?uzAP92cWUSdFm91P0kl9vWU6BkRNej0GocUQ2KFIMSABHFISWfS+wviyZp/y?= =?us-ascii?Q?zmTqG3baBgsxxXMBl4hyzbSXPZK97fAcjfcSHGkZxQteqcLhl7mlGvlE4FwH?= =?us-ascii?Q?ubZiEAh8AfVJpJhGHa2b19nQcni1sKsU3psI5X1fRYUuQdsc/2B10aGwpEY9?= =?us-ascii?Q?5NQ0gGUkckjGlIYZXeJU56SRwDtGusrgR9L7yL/OluVGQ/qAu/LjZOIVn42h?= =?us-ascii?Q?/BMwBEubZA41lFVusMonMmJ2KbdS0eNSOXgMOdfTt+04H9sd/39lNJV6j7XH?= =?us-ascii?Q?kiDFgFKQIMNLwPjIUbO0M/ePgMwdmoER2ce3bD2pmjjegjywonLpsPH8BpgL?= =?us-ascii?Q?Q9GiQske646kRROuju/UT6D4UBQL1VA50YIagpP0NOluswGwGzX3pvPImnog?= =?us-ascii?Q?0bXrRF2IbGuCtxkZrKYOtoeIFU32yC6+gHPkwUZgsnX2rTpg5JLYCDppJ46a?= =?us-ascii?Q?9cEG0B9vRGL1HtZFqY6j7tjvxh11ARhO1/H/EXBNngECvC90h1V7hM+9uFzl?= =?us-ascii?Q?Ii69InVTI7EcTCTPMTqmCNxx5eTIZwo6mYViLlo+SJafJDJpLFrhGp0qQDBr?= =?us-ascii?Q?f0sw8+A3ULUwBel0tgjtn9+qpL9BMPQuAPROAKKQ9ouB26gZaIztSlJLE6dr?= =?us-ascii?Q?ymcMBYS/bgKd6n0XVh+C+KijIXPlxWnDUFtEXonFweHaZ28VmQnR6pB3wFh0?= =?us-ascii?Q?3ZvXCvBDD83asBHYx8bDH57OHSkjz9fbzZwif6mNfkr2PGruOMcfp8dDwR2a?= =?us-ascii?Q?olu25XxXBz2TkVmHAyhzYT1xTnFZ/ejSEm5+kMz6DJh6U4YaPxJ8fX7rtjjN?= =?us-ascii?Q?3MxD9tor6Yv57BjjcM2TV8wvBloKzOZJnfNxvEE1ebKcix61jjITH/zPAUuD?= =?us-ascii?Q?/Y43KgmnXMXlRteVqkUJ1YZFqcwlIe+WGG+8/XF6/93T+ReWFYExY/FNyChp?= =?us-ascii?Q?wG3GKLySNpWek0AO0Nqu79emWtxMWlSUcyNTQZJah3hCP+hjbAH1jfx6DOxr?= =?us-ascii?Q?eF5iS3GJrioW/eFp431GTP/L9m9vnf7diGkBIq9d87l8AE+0SGfBMVGBDA9T?= =?us-ascii?Q?u7z5vgkZMPYhUwCLqytdyAguMzkOA+fMZFJHB0Uk0wOhW9XUi3hsSKFGeJl5?= =?us-ascii?Q?yCH66Vnw+tpIAkxBynfUv4T60YXluahd02keGK9u1FE7wWQ3GUxAex3pwnwC?= =?us-ascii?Q?3wqzMqQqftjfC2+C8H6cLGcy4VI9WN8lpdL6bM83M/3y6w=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 224e6d8f-3f28-44f9-bc16-08d989c62fac X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Oct 2021 19:10:54.6861 (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: lR2412qrpFDKLCRLUce3o8cABNQGB3jtcHjJGrXWrpmh7Z77qwWQIFLDhkWjvJt2 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5125 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 07, 2021 at 12:11:27PM -0700, Jacob Pan wrote: > Hi Barry, > > On Thu, 7 Oct 2021 18:43:33 +1300, Barry Song <21cnbao@gmail.com> wrote: > > > > > Security-wise, KVA respects kernel mapping. So permissions are better > > > > enforced than pass-through and identity mapping. > > > > > > Is this meaningful? Isn't the entire physical map still in the KVA and > > > isn't it entirely RW ? > > > > Some areas are RX, for example, ARCH64 supports KERNEL_TEXT_RDONLY. > > But the difference is really minor. > That brought up a good point if we were to use DMA API to give out KVA as > dma_addr for trusted devices. We cannot satisfy DMA direction requirements > since we can't change kernel mapping. It will be similar to DMA direct > where dir is ignored AFAICT. Right. Using the DMA API to DMA to read only kernel memory is a bug in the first place. > Or we are saying if the device is trusted, using pass-through is allowed. > i.e. physical address. I don't see trusted being relavent here beyond the usual decision to use the trusted map or not. 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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Thu, Oct 07, 2021 at 12:11:27PM -0700, Jacob Pan wrote: > Hi Barry, > > On Thu, 7 Oct 2021 18:43:33 +1300, Barry Song <21cnbao@gmail.com> wrote: > > > > > Security-wise, KVA respects kernel mapping. So permissions are better > > > > enforced than pass-through and identity mapping. > > > > > > Is this meaningful? Isn't the entire physical map still in the KVA and > > > isn't it entirely RW ? > > > > Some areas are RX, for example, ARCH64 supports KERNEL_TEXT_RDONLY. > > But the difference is really minor. > That brought up a good point if we were to use DMA API to give out KVA as > dma_addr for trusted devices. We cannot satisfy DMA direction requirements > since we can't change kernel mapping. It will be similar to DMA direct > where dir is ignored AFAICT. Right. Using the DMA API to DMA to read only kernel memory is a bug in the first place. > Or we are saying if the device is trusted, using pass-through is allowed. > i.e. physical address. I don't see trusted being relavent here beyond the usual decision to use the trusted map or not. Jason _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu