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Thu, 13 Aug 2026 02:40:03 -0700 From: To: , , , , , , , , , , , , , , , , , , , , CC: , , , , , , , , , , , Subject: [PATCH v4 19/27] vfio/cxl: Keep the HDM decoder block off the direct BAR mapping Date: Thu, 13 Aug 2026 15:06:23 +0530 Message-ID: <20260813093631.2288172-20-mhonap@nvidia.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260813093631.2288172-1-mhonap@nvidia.com> References: <20260813093631.2288172-1-mhonap@nvidia.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN1PEPF00004687:EE_|DS5PPF8002542C7:EE_ X-MS-Office365-Filtering-Correlation-Id: 76aa5285-9e79-4b2e-c690-08def91ee9c8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|36860700016|1800799024|7416014|376014|82310400026|10067099003|11063799006|56012099006|22082099003|18002099003|921020; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: sHgP1buHzNwVkboliG6bqYUYDhWtJPG5vk7sfamL7H7odXqHVdJd4diKAw3271mj4JCR1+h9GXYoj+ycPlnyYKAcIw3RGXl2J9kbmx4bcp5+Y6GOwZ0/1J3wHGbNQ2NtDtduSs1oU7G8J+1mW8fP17Cq7dgTHMV1CRM+sUDEj5uVpf+a+Dy9klwzGIm+6tBsyVpDCspcji3Mt0CAW3UoKghUPy7aidxCaIqezxecJstqXCidp1ZuGB+hbkVieEs7bwEpGomr2vwlnRV0jwNYQ/GmqrnWNv7ITF/+MeH59P/VhhzDt5vaSIQNtIQ+nB9erR2ayeCljul95WWLe5RlGtN0NUxS0+wmfrc/ocXIAU4/db9W0xR/Iyv7a95stMKCdnNY3sFXbeaixxo0/BBuVZQ8oFftHvD78vNibo8Iwmcc6Fz8f27qHQkEQw0J4XQe X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Aug 2026 09:40:29.7427 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 76aa5285-9e79-4b2e-c690-08def91ee9c8 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF00004687.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS5PPF8002542C7 From: Manish Honap vfio-cxl owns the whole component BAR and serves the HDM decoder block through a trapped region that runs the commit FSM against a shadow. Left directly mmappable, the same block would let userspace reach the physical decoder and move the host physical window. Exclude it from the BAR mmap so the trap is the only path to it. Signed-off-by: Manish Honap --- drivers/vfio/pci/cxl/vfio_cxl_core.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c b/drivers/vfio/pci/cxl/vfio_cxl_core.c index 07047646edde..f91f6eb8b8fb 100644 --- a/drivers/vfio/pci/cxl/vfio_cxl_core.c +++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c @@ -339,6 +339,14 @@ static int vfio_cxl_init_device(struct vfio_pci_core_device *vdev) cxl->hdm_len = pdev->hdm->hdm_size; + /* + * The HDM decoder block is served from the trapped component-register + * region. Keep it out of the guest's direct BAR mapping so the physical + * decoder, which governs host memory decode, cannot be reprogrammed. + */ + vfio_pci_core_set_mmap_exclude(vdev, pdev->hdm->hdm_bar, + pdev->hdm->hdm_offset, cxl->hdm_len); + ret = cxl_set_capacity(&cxl->cxlds, hdm_size); if (ret) return ret; -- 2.25.1