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Sampat" , Scott Soule Cheloha , Ackerley Tng , Fuad Tabba Subject: [RFC PATCH kernel 09/17] dma/swiotlb: Force shared DMA for allocatios from SWIOTLB Date: Wed, 16 Sep 2026 21:51:49 +1000 Message-ID: <20260916115159.1938195-10-aik@amd.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260916115159.1938195-1-aik@amd.com> References: <20260916115159.1938195-1-aik@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: satlexmb08.amd.com (10.181.42.217) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN1PEPF00018548:EE_|IA0PPF6E99B1BC1:EE_ X-MS-Office365-Filtering-Correlation-Id: 0c3e0d42-9d65-43b7-68d7-08df13e9c79b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|82310400026|7416014|32650700020|23010399003|36860700016|18002099003|22082099003|10067099003|56012099006|11063799006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(376014)(1800799024)(82310400026)(7416014)(32650700020)(23010399003)(36860700016)(18002099003)(22082099003)(10067099003)(56012099006)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: N+QQCCWsHa7bqeHcyE9nTBdDa+bifDbun1axL/Jp+ouegH1jwRNDqGgZk9TnDMM0NkTrcFPDnH+mykQQ0BMSQxgY6hyIlPAIwKpGIAO+SlfWu1uY4kl2tIJYheErrmKT6AiYJLReu57IKXwx/n1iCmnQ/1sNR6Qx9rksJF+r7pSItlxQmXGUdxLCcqTz478u3FI20fTD5nJ7nyf37O4NpIHYbh3xpHya/3WGmaKBccRqqiF3pB0m10k//KIaBQcKbtyc1vuVtbYs5hu5q1T8AzJnqKlTvvdi8qtlFANfaGhlnhwnJA1w32iuN27yG1NExvnhRTcGPXtxAlggmbrjRRMf0VoeT0wKRj6X5ZhXvBNi9Egyrep6YAHcKOkokxnLq1riiT/QoWOY9upXNI8KANCUiE8B4qkM6/pLLtlzFqVPEro4k8b8NJ5zTk6WRHf0 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Sep 2026 11:58:10.6516 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0c3e0d42-9d65-43b7-68d7-08df13e9c79b X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF00018548.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PPF6E99B1BC1 SWIOTLB allocations are always decrypted but the DMA layer is unaware of those and will miss to adjust the DMA handle. Force __DMA_ATTR_ALLOC_CC_SHARED if SWIOTLB is used for memory allocations. This will be exploited by AMD SEV guest vTOM feature where DMA handles of shared memory have some high bit set (not to be confused with the Cbit). Signed-off-by: Alexey Kardashevskiy --- kernel/dma/direct.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index da665ca22d5c..dacf513d45fd 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -273,13 +273,14 @@ void *dma_direct_alloc(struct device *dev, size_t size, } if (is_swiotlb_for_alloc(dev)) { - page = dma_direct_alloc_swiotlb(dev, size, attrs); + page = dma_direct_alloc_swiotlb(dev, size, attrs | __DMA_ATTR_ALLOC_CC_SHARED); if (page) { /* * swiotlb allocations comes from pool already marked * decrypted */ mark_mem_decrypt = false; + attrs |= __DMA_ATTR_ALLOC_CC_SHARED; goto setup_page; } return NULL; -- 2.55.0