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Thu, 30 Jul 2026 21:05:16 +0000 Received: from CY1PR12MB9601.namprd12.prod.outlook.com ([fe80::cd76:b497:475f:4de3]) by CY1PR12MB9601.namprd12.prod.outlook.com ([fe80::cd76:b497:475f:4de3%4]) with mapi id 15.21.0270.012; Thu, 30 Jul 2026 21:05:16 +0000 Date: Thu, 30 Jul 2026 18:05:14 -0300 From: Jason Gunthorpe To: "Aneesh Kumar K.V" Cc: Mostafa Saleh , iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org, Jiri Pirko , Michael Kelley Subject: Re: [PATCH v8 15/23] dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks Message-ID: References: <20260717180442.110954-1-aneesh.kumar@kernel.org> <20260717180442.110954-16-aneesh.kumar@kernel.org> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?bgcwd4SPDJiAMmLE5rq7qpg5+zS3l8ygwKzLXcb03srwU62dhbRWmvKv+cYz?= =?us-ascii?Q?nCM712X4wFSu6KCvXptVtKR3mVjwfYn6YWSo72P5Jowz+d1RlLZHP2ulo+lK?= =?us-ascii?Q?IVwPPJ1L/8blxas0Lh0XfVkF1pvKt0fXtc092PXw9UTDmUo4BO97hPmvEJaj?= =?us-ascii?Q?Wy92us4SFglw4kTgFkbBsAZUMl06MHhyXRMMMX5AQWtVvuyuxKPQahEWPby1?= =?us-ascii?Q?j7Lgyx5fIkBc28WjvgI+IWCBs+oIjXCLpKmZJjt6qjCBWfmc2ttvbTqofQFr?= =?us-ascii?Q?rGUfrRuCAR3WCRtHifGGxEnnDyfyXqf/EL1V10Gx+0aDA5qL23KHdchKtd9j?= =?us-ascii?Q?/30O3+QtttnUu3f827kCvNfyJsmuFZg2AbaO3NWyEEIEfFCvg7DAYe5rtOr+?= =?us-ascii?Q?GIeQ320yVrVJMy3GnQzUljqaiQEzi9yXwrYDqWPjluRR8ZTBuxCVpJcWY8M1?= =?us-ascii?Q?Lo8iZEOi6IbuO1ZjUNLdnYc19Vc1UFltOrDtq4NhRNBQ8o9s+6PvNwBaeEaW?= =?us-ascii?Q?AY5guiysCoA8oTMqrv1T3m+Gwb+guy1D9iYEoHTfsq2Be3K46kTq/0JZWMk8?= =?us-ascii?Q?BsXq4KfaPSqRTthHyonTbGPCOfoWrWkuDJmLf9aji/cO9P2ZmkxlNM0JK5JL?= =?us-ascii?Q?BByq2BobzK+eZaCRwiu+OXm+nISmKKIgaVQQBOZsTO0NozvrjB5o4ajoZSPk?= =?us-ascii?Q?cBOs8uQOlqQVKFssl3qwvNXzEvxZSYlmVRUh2H6E77/cC5qZruR/LG6vo+NP?= =?us-ascii?Q?jmv0z4aqspgM0XsRNqw2a448bbf+oqReUzzdLcseCyztEqM4UW+ixIVrs/sS?= =?us-ascii?Q?4q/qzcO0DHIE6+5TFkA9YN9kam7dx7bM7eouGDRuTanLga4umoR6RcjaG8EN?= =?us-ascii?Q?74dFJvi56pGNIUNASrw5Q5kiK3szFqDca6yNcAifT08oO7QWl9awGNp5GY6L?= =?us-ascii?Q?Kn7k+SNHnJFE6vPiG5gcvQQZTTilNlfmfWQOvt/ZOUGnT/bKnderBIPLxXrx?= =?us-ascii?Q?tTe8OnNvFNXN5UGmUrQUHX/nvdEzaKVflreg9RCQG/T4tiVFm3JmIS1OtmwX?= =?us-ascii?Q?iWb0hMT8eygyVdYWu/uJARJ6k33qPBjpHjexhHFvlAZiCxi7Qq+F+bEhjTRu?= =?us-ascii?Q?BB2ErkIUCtKkfvU01Agt4nW6jL/tbIAa0RJz/3olzSSBOdIQ1xZez9M1TfUw?= =?us-ascii?Q?KdUeH46NKc8l+kyA4GBPWY/yGlwEDTXRPxOz7FAfl37pzgxln4lp9N0Jx79D?= =?us-ascii?Q?UYA6tLCI9c6TIkQB7FrPAAhq+phSGfd+aXVjt1OWR+iEt3ZnpMSPNnylDLp5?= =?us-ascii?Q?xKuq9e0PDcsOjbk2zCpV2r28uxPyXyyxEoN74ZvAyGsaYPXaVvOYkQN+JVKN?= =?us-ascii?Q?pb0mp7VfAgJnOZ7e00U7h6FnhdkCm8kqegudB14tNjxrWI6bB2RNuz+ITaRk?= =?us-ascii?Q?CSJZ2xDXM/VbVvEsPNR1h91yxVqap3DB79nj6zPYYsZCwLwz2FXkuKwCsM0L?= =?us-ascii?Q?CdzKEpoOtKsB1WFdo4RZZJPZ8m7n0690sxp7VZEEXHFIJFx54HYE9XTP/Gl8?= =?us-ascii?Q?q4vxT6HmBnNexunKSFyFv8/hH5/pg8VfaREBLvfEGv13CD1+7p8AX8Sdz1ak?= =?us-ascii?Q?WfcxkQ8jAzvdL6JoTzMYl3WrxPURPk3xQSZllUggMN+gypCg0EDrafBWZHTQ?= =?us-ascii?Q?Q31i40V87qIlanqJDeK9S1tdoIgyxtmUbf096axJKLy/hOaX?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 81eb01ee-6a22-4efa-7e32-08deee7e410d X-MS-Exchange-CrossTenant-AuthSource: CY1PR12MB9601.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jul 2026 21:05:15.9773 (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: 0TgSSlFZ+GG5NyHGxa4z9KuvQ+BdXqxoFl130lSXeL4MBISZOAOdTE3DePxVAkOo X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR12MB8962 On Wed, Jul 29, 2026 at 02:39:08PM +0530, Aneesh Kumar K.V wrote: > Mostafa Saleh writes: > > >> static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, > >> - bool is_ram) > >> + bool is_ram, unsigned long attrs) > >> { > >> dma_addr_t end = addr + size - 1; > >> > >> if (addr == DMA_MAPPING_ERROR) > >> return false; > >> + /* > >> + * The DMA address was derived from encrypted RAM, but this device > >> + * requires unencrypted DMA addresses. Treat it as not DMA-capable > >> + * so the caller can fall back to a suitable SWIOTLB pool. > >> + */ > >> + if (!(attrs & DMA_ATTR_CC_SHARED) && force_dma_unencrypted(dev)) > >> + return false; > >> + > > > > I guess it does not make sense to check the other way? I'd be worried if > > some a confidential device uses shared memory which might leak info. > > > > From the perspective of the dma_capable() check, this should be allowed; > that is, a trusted device is permitted to access shared memory. Right, we have use cases that require confidential devices to use shared memory we cannot block it at the DMA layer. It would be a reasonable DMA debugging to block shared memory without the DMA ATTR CC SHARED. Jason