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pr=C From: Stefano Stabellini To: CC: , , , , , , Vikram Garhwal , "Stefano Stabellini" , Henry Wang Subject: [PATCH v5 7/7] docs: Add device tree overlay documentation Date: Thu, 23 May 2024 19:18:14 -0700 Message-ID: <20240524021814.2666257-7-stefano.stabellini@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: None (SATLEXMB04.amd.com: stefano.stabellini@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B374:EE_|SA3PR12MB7808:EE_ X-MS-Office365-Filtering-Correlation-Id: e4961a22-ac01-47d0-80d5-08dc7b97d2f3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230031|1800799015|376005|82310400017|36860700004; 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:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230031)(1800799015)(376005)(82310400017)(36860700004);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 May 2024 02:18:38.8750 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e4961a22-ac01-47d0-80d5-08dc7b97d2f3 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B374.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB7808 From: Vikram Garhwal Signed-off-by: Vikram Garhwal Signed-off-by: Stefano Stabellini Signed-off-by: Henry Wang --- docs/misc/arm/overlay.txt | 82 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 docs/misc/arm/overlay.txt diff --git a/docs/misc/arm/overlay.txt b/docs/misc/arm/overlay.txt new file mode 100644 index 0000000000..0a2dee951a --- /dev/null +++ b/docs/misc/arm/overlay.txt @@ -0,0 +1,82 @@ +# Device Tree Overlays support in Xen + +Xen experimentally supports dynamic device assignment to running +domains, i.e. adding/removing nodes (using .dtbo) to/from Xen device +tree, and attaching them to a running domain with given $domid. + +Dynamic node assignment works in two steps: + +## Add/Remove device tree overlay to/from Xen device tree + +1. Xen tools check the dtbo given and parse all other user provided arguments +2. Xen tools pass the dtbo to Xen hypervisor via hypercall. +3. Xen hypervisor applies/removes the dtbo to/from Xen device tree. + +## Attach device from the DT overlay to domain + +1. Xen tools check the dtbo given and parse all other user provided arguments +2. Xen tools pass the dtbo to Xen hypervisor via hypercall. +3. Xen hypervisor attach the device to the user-provided $domid by + mapping node resources in the DT overlay. + +# Examples + +Here are a few examples on how to use it. + +## Dom0 device add + +For assigning a device tree overlay to Dom0, user should firstly properly +prepare the DT overlay. More information about device tree overlays can be +found in [1]. Then, in Dom0, enter the following: + + (dom0) xl dt-overlay add overlay.dtbo + +This will allocate the devices mentioned in overlay.dtbo to Xen device tree. + +To assign the newly added device from the dtbo to Dom0: + + (dom0) xl dt-overlay attach overlay.dtbo 0 + +Next, if the user wants to add the same device tree overlay to dom0 +Linux, execute the following: + + (dom0) mkdir -p /sys/kernel/config/device-tree/overlays/new_overlay + (dom0) cat overlay.dtbo > /sys/kernel/config/device-tree/overlays/new_overlay/dtbo + +Finally if needed, the relevant Linux kernel drive can be loaded using: + + (dom0) modprobe module_name.ko + +## DomU device add/remove + +All the nodes in dtbo will be assigned to a domain; the user will need +to prepare the dtb for the domU. For example, the `interrupt-parent` +property of the DomU overlay should be changed to the Xen hardcoded +value `0xfde8`, and the xen,reg property should be added to specify the +address mappings. If xen,reg is not present, it is assumed 1:1 mapping. +Below assumes the properly written DomU dtbo is `overlay_domu.dtbo`. + +For new domains to be created, the user will need to create the DomU +with below properties properly configured in the xl config file: +- `iomem` +- `passthrough` (if IOMMU is needed) + +User will also need to modprobe the relevant drivers. For already +running domains, the user can use the xl dt-overlay attach command, +example: + + (dom0) xl dt-overlay add overlay.dtbo # If not executed before + (dom0) xl dt-overlay attach overlay.dtbo $domid + (dom0) xl console $domid # To access $domid console + +Next, if the user needs to modify/prepare the overlay.dtbo suitable for +the domU: + + (domU) mkdir -p /sys/kernel/config/device-tree/overlays/new_overlay + (domU) cat overlay_domu.dtbo > /sys/kernel/config/device-tree/overlays/new_overlay/dtbo + +Finally, if needed, the relevant Linux kernel drive can be probed: + + (domU) modprobe module_name.ko + +[1] https://www.kernel.org/doc/Documentation/devicetree/overlay-notes.txt