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GET /api/1.1/patches/2229147/?format=api
{ "id": 2229147, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2229147/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260427181235.3003865-10-mhonap@nvidia.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/1.1/projects/14/?format=api", "name": "QEMU Development", "link_name": "qemu-devel", "list_id": "qemu-devel.nongnu.org", "list_email": "qemu-devel@nongnu.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20260427181235.3003865-10-mhonap@nvidia.com>", "date": "2026-04-27T18:12:35", "name": "[RFC,9/9] vfio/listener: Skip DMA mapping for VFIO-owned RAM-device regions", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "b571d69b9a238dc0354a8f758cf2b01f367f6bfb", "submitter": { "id": 92895, "url": "http://patchwork.ozlabs.org/api/1.1/people/92895/?format=api", "name": "Manish Honap", "email": "mhonap@nvidia.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260427181235.3003865-10-mhonap@nvidia.com/mbox/", "series": [ { "id": 501717, "url": "http://patchwork.ozlabs.org/api/1.1/series/501717/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=501717", "date": "2026-04-27T18:12:35", "name": "QEMU: CXL Type-2 device passthrough via vfio-pci", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/501717/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2229147/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2229147/checks/", "tags": {}, "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=RNK4V1H2;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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helo=mail.nvidia.com; pr=C", "permerror client-ip=2a01:111:f403:c10c::1;\n envelope-from=mhonap@nvidia.com;\n helo=SA9PR02CU001.outbound.protection.outlook.com" ], "From": "<mhonap@nvidia.com>", "To": "<alwilliamson@nvidia.com>, <skolothumtho@nvidia.com>, <ankita@nvidia.com>,\n <mst@redhat.com>, <imammedo@redhat.com>, <anisinha@redhat.com>,\n <eric.auger@redhat.com>, <peter.maydell@linaro.org>,\n <shannon.zhaosl@gmail.com>, <jonathan.cameron@huawei.com>,\n <fan.ni@samsung.com>, <pbonzini@redhat.com>, <richard.henderson@linaro.org>,\n <marcel.apfelbaum@gmail.com>, <clg@redhat.com>, <cohuck@redhat.com>,\n <dan.j.williams@intel.com>, <dave.jiang@intel.com>,\n <alejandro.lucero-palau@amd.com>", "CC": "<vsethi@nvidia.com>, <cjia@nvidia.com>, <targupta@nvidia.com>,\n <zhiw@nvidia.com>, <kjaju@nvidia.com>, <linux-cxl@vger.kernel.org>,\n <kvm@vger.kernel.org>, <qemu-devel@nongnu.org>, <qemu-arm@nongnu.org>,\n \"Manish Honap\" <mhonap@nvidia.com>", "Subject": "[RFC 9/9] vfio/listener: Skip DMA mapping for VFIO-owned RAM-device\n regions", "Date": "Mon, 27 Apr 2026 23:42:35 +0530", "Message-ID": "<20260427181235.3003865-10-mhonap@nvidia.com>", "X-Mailer": "git-send-email 2.25.1", "In-Reply-To": "<20260427181235.3003865-1-mhonap@nvidia.com>", "References": "<20260427181235.3003865-1-mhonap@nvidia.com>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "Content-Type": "text/plain", "X-Originating-IP": "[10.126.230.37]", "X-ClientProxiedBy": "rnnvmail202.nvidia.com (10.129.68.7) To\n rnnvmail201.nvidia.com (10.129.68.8)", "X-EOPAttributedMessage": "0", "X-MS-PublicTrafficType": "Email", "X-MS-TrafficTypeDiagnostic": "CY4PEPF0000EDD0:EE_|BL3PR12MB6522:EE_", "X-MS-Office365-Filtering-Correlation-Id": "00024a03-dfee-4293-5e99-08dea488e204", "X-MS-Exchange-SenderADCheck": "1", "X-MS-Exchange-AntiSpam-Relay": "0", "X-Microsoft-Antispam": "BCL:0;\n ARA:13230040|1800799024|82310400026|36860700016|376014|7416014|921020|56012099003|18002099003|22082099003;", "X-Microsoft-Antispam-Message-Info": "\n mni4ZTlaNXFIJIicT8a0lBKLrUxIbdjXGVAtaxRuXSuMx7ctU8GXmCGIHtr7y+r3IgT9yVQKR1e+tCCRDf4zeh0NreG4cXe7DZe4f3ZMj9w0+salXzBHbVCZqRsxdjOuAvYCI8iGgYE58ZIVfBg6QJY25vHIownWmVy20GBPSSDmuQNq1EGzoGhVuVP5hJXSqix6gf5H8L8VZoaSxRbxEkJuHGvb/mWNMw8S16U9j3NluxPCX9LJhq2Jygb3oqHKCja1SpiD3lGfQeYPosmJvIOegMOzcTBt0o34bzphmsDMkvPCT5oEeYpkvRcTOu6mOK6HbenXKgEJnE1DgYuDhuWdvEL+Rd1YcpTUEyn4KmSt5TWUwQM+Kb6hJ7HyIWLnpH6c8mso/LzEEmw8taHHzr0l0inKZc+DvdaTFqwHWl1tpiK8hCBR3rWDR5tFkp537AENZaWEUfyIF8+C/P+kuvUUtc3Q0DHYvz2xx++GwiAiflR/U4pJ/ciR0JiCZpHdj+0OA3MeO2T+yR1RVR9/WsyHnyKoKc8XbaYtM0CJjPklEIy4kv8iNl0xIM4hLJmGAM4oF1XcSVMByV/sA3cw5KN1re/seucYHapedTTbCoT6m8z5U+Fqea0PqDfCt8XI1vB91utTsn9qxFC9Uf+/8bboM95COW+b8N2OnkhlX+sUHYHFe08gtY6CgPh3Gn3Ux+MSQH3nMnHEvRgCrk5gQSAXUAjk3UpUgowIgw9la7Bibek4Yc9Tq97ftji0C2nFf30FpY9WH52ct4T90K8dKNnZ5i2d8/yBWefX4fJZP4EdC4apY+VHa4OEzu/RYG47", "X-Forefront-Antispam-Report": "CIP:216.228.117.160; CTRY:US; LANG:en; SCL:1;\n SRV:;\n IPV:NLI; SFV:NSPM; H:mail.nvidia.com; PTR:dc6edge1.nvidia.com; CAT:NONE;\n SFS:(13230040)(1800799024)(82310400026)(36860700016)(376014)(7416014)(921020)(56012099003)(18002099003)(22082099003);\n DIR:OUT; SFP:1101;", "X-MS-Exchange-AntiSpam-MessageData-ChunkCount": "1", "X-MS-Exchange-AntiSpam-MessageData-0": "\n iJkJVTKPV21OueNuCeWULUALlNIcbEcEQSxGlRLVfaPS6+zSXVtp7vaktr9R0g3N5PJYCFDKiNUeu4SiVb05GpI3R5FdpGjCY6mrR11Sj/gQxoFNi/0BtSS8PfiY/nKE3JCMG5tMSJBc8Kd5CeaJby+DBu99cH3r99pI+0E8GZlorpLqpGs/cnTo26MfIem57vewvTA+BGuB4lqsobU3Q43atjh4gDCmMrp2QE66pF1CSozAtXE0vrfak9pBhnA8zH/N+9FHAx6R3UkIZj5s8LIWtoaO080Hv8UdiAyPuWbqlqSuUcKaWzXOzP2mebQ74md9zqS05OA6+2yTHFAOfvPq60IR+031ghl9fX5maXkE+FOKXdLqKEq2FDeBBVdFFUYiCvw7rcYnvmWFaZ3QI+uXORyNJ2UBxvZMT4zBw9/yf7jNI+GTp3c/b2BxKu9k", "X-OriginatorOrg": "Nvidia.com", "X-MS-Exchange-CrossTenant-OriginalArrivalTime": "27 Apr 2026 18:14:54.6718 (UTC)", "X-MS-Exchange-CrossTenant-Network-Message-Id": "\n 00024a03-dfee-4293-5e99-08dea488e204", "X-MS-Exchange-CrossTenant-Id": "43083d15-7273-40c1-b7db-39efd9ccc17a", "X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp": "\n TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a; Ip=[216.228.117.160];\n Helo=[mail.nvidia.com]", "X-MS-Exchange-CrossTenant-AuthSource": "\n CY4PEPF0000EDD0.namprd03.prod.outlook.com", "X-MS-Exchange-CrossTenant-AuthAs": "Anonymous", "X-MS-Exchange-CrossTenant-FromEntityHeader": "HybridOnPrem", "X-MS-Exchange-Transport-CrossTenantHeadersStamped": "BL3PR12MB6522", "X-Spam_score_int": "-10", "X-Spam_score": "-1.1", "X-Spam_bar": "-", "X-Spam_report": "(-1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n FORGED_SPF_HELO=1, SPF_HELO_PASS=-0.001,\n SPF_NONE=0.001 autolearn=no autolearn_force=no", "X-Spam_action": "no action", "X-Mailman-Approved-At": "Mon, 27 Apr 2026 15:57:41 -0400", "X-BeenThere": "qemu-devel@nongnu.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "qemu development <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "From: Manish Honap <mhonap@nvidia.com>\n\nvfio_container_region_add() attempts an IOMMU DMA mapping for every\nRAM section that enters the guest address space. For VFIO mmap-backed\nregions (PCI BAR windows, CXL.mem regions), this mapping always fails:\nthe backing VMAs carry VM_IO | VM_PFNMAP flags and pin_user_pages()\nrefuses to pin VM_IO pages, so IOMMU_IOAS_MAP returns -EFAULT.\n\nCPU access to these regions goes through KVM Stage-2 page faults\nindependently of the SMMU/IOMMU, so no IOMMU entry is required for\ncorrect operation.\n\nAdd an early return for RAM-device sections owned by a VFIO device.\nvfio_get_vfio_device(memory_region_owner(section->mr)) returns non-NULL\nfor any mmap subregion created by vfio_region_mmap(), since\nmemory_region_init_ram_device_ptr() propagates the VFIOPCIDevice owner\nfrom the containing region. Matching on ownership covers both normal\nPCI BAR windows and CXL.mem regions uniformly; non-VFIO RAM-device\nregions such as NVDIMMs are unaffected and continue through the normal\nmapping path.\n\nSigned-off-by: Manish Honap <mhonap@nvidia.com>\n---\n hw/vfio/listener.c | 14 ++++++++++++++\n 1 file changed, 14 insertions(+)", "diff": "diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c\nindex 31c3113f8f..46cad18357 100644\n--- a/hw/vfio/listener.c\n+++ b/hw/vfio/listener.c\n@@ -608,6 +608,20 @@ void vfio_container_region_add(VFIOContainer *bcontainer,\n pgmask + 1);\n return;\n }\n+\n+ /*\n+ * VFIO MMAP backed regions (CXL.mem) uses VM_IO | VM_PFNMAP VMAs\n+ * backed by physical device addresses. Skip vfio_container_dma_map\n+ * as mapping is not needed for this region.\n+ */\n+ if (vfio_get_vfio_device(memory_region_owner(section->mr))) {\n+ trace_vfio_listener_region_add_no_dma_map(\n+ memory_region_name(section->mr),\n+ section->offset_within_address_space,\n+ int128_getlo(section->size),\n+ pgmask + 1);\n+ return;\n+ }\n }\n \n ret = vfio_container_dma_map(bcontainer, iova, int128_get64(llsize),\n", "prefixes": [ "RFC", "9/9" ] }