From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from PH7PR06CU001.outbound.protection.outlook.com (mail-westus3azon11010057.outbound.protection.outlook.com [52.101.201.57]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0267F2989B5; Fri, 21 Nov 2025 12:17:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.201.57 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763727447; cv=fail; b=uzK3L/HUwQdt4tFwK8lnBTb/DuGp4E8liPP9JroOcZf3j0L/LiQKGn9A7wgh1Se0qUCTLF5mhj78k41wtmxrcufz3sRa+HfBQUXSzbKs5Yr3MCwkXwmocVbA/mDWaXZ8P9G7Ja/UlNwP2Q1jBuEcPuQ+vlJPdtU7+5ek4Ih7Q8M= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763727447; c=relaxed/simple; bh=diRLHIMg5nqxw2Ex+F3YACDiMbilHxzTCHq/m1fNEj8=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WLqWgx3K1rgMUtRusKVPHlbg60pDvOSOeSAynPxUJcez2i/yWeH2kzKThPDahQLB6toPNexvXJZmu1ofPRYu5SI8KrouVPm2zO+8hQIFSW7OQuuRdhqqdHwcY4aeKCcE6MJKWi3xOsAyhb5LrIOwiKLuMg8xQt6fSTQwnO6scdo= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=pSU6xCWA; arc=fail smtp.client-ip=52.101.201.57 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="pSU6xCWA" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=fA50EdhaqJnhIpN7uyWavW6lS0vQUudO0sDNY6hPBbWLFGbaza+b9L2Sp07wUfor7otdeX2GlnQ7wKa14KXnlh66LdSPwtcVa9qKpwwxyYSbkKL9Jf4w69yFfPw5WtMwquiHkPRlIzYILD5BoHXvIUkdFtttiWTmXsPIvN+zBG2T48kyJVjyx4WsWh94OQvZKzbwrYwO+4RZ6m3W1Be/WxomnuSowapSm8gFaJedgNB8ns6R8p9LBtCcgLLXxyr1poaIwIraz2pRMD5YLp6mJeFvskIb7Z2lrgtNu66YlJE2l1VAbo9CD2fx/E265rnBzIa9fvDrE8zTmwK6BPq0EA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=Fd34vCUBOirASchP9G/JWEw4nKEapGeBMjpsSkx1LMo=; b=x1T5mxyTT7AsTgYQoWc1m+/TW/YVVV/urCNMHOUAn8zc1OFYPPJAUJWYt2sLm8hTC6xg8wOd+vp0O/nEhoytIvSznJKPXUDk9fe64+kcd9PJjzWbmV3j+52Cfd9E2/B7A0NZkAusZvoJuPDe5vkx1QCc5QFVC4Z3pHHIkB3Ydke1RGNjiGPILVc09nqn8OyL7AP8BPzLCc5CyU4txIUudwgASdi9zNBL5G1cQURBRkgqqvZQ8UMftu+PwbUgtRT73Xqx6OCS1n1rzTTWU8+Xcyw4rd60JSi+jLTD+BR+UH6nsYfpwais+g6ksFaDpRiogiyxcYW8qnYJTiKZ74leXA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 165.204.84.17) smtp.rcpttodomain=intel.com smtp.mailfrom=amd.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=amd.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Fd34vCUBOirASchP9G/JWEw4nKEapGeBMjpsSkx1LMo=; b=pSU6xCWArVivz6oGBvasScMxw6SwxOKsGuUNc21MWd/LHGj23wF2RqzLlZ9Rh1NX8DsfKXHfB4DgOA9nFB4hILBZT2eKl9CAqkBcs8KM0PI+YGpNZ4z9mcWbWpqCxrFdyoeWt4SLCPI+piBjibpAPzwjBzBLOGA9iIsgnFSr3+Y= Received: from BN9PR03CA0760.namprd03.prod.outlook.com (2603:10b6:408:13a::15) by DS0PR12MB6559.namprd12.prod.outlook.com (2603:10b6:8:d1::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9343.14; Fri, 21 Nov 2025 12:17:18 +0000 Received: from BN3PEPF0000B36F.namprd21.prod.outlook.com (2603:10b6:408:13a:cafe::26) by BN9PR03CA0760.outlook.office365.com (2603:10b6:408:13a::15) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.9343.12 via Frontend Transport; Fri, 21 Nov 2025 12:17:08 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by BN3PEPF0000B36F.mail.protection.outlook.com (10.167.243.166) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9366.1 via Frontend Transport; Fri, 21 Nov 2025 12:17:17 +0000 Received: from rric.localdomain (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Fri, 21 Nov 2025 04:17:13 -0800 From: Robert Richter To: Alison Schofield , Vishal Verma , Ira Weiny , Dan Williams , Jonathan Cameron , Dave Jiang , Davidlohr Bueso , Jonathan Corbet CC: , , Gregory Price , "Fabio M. De Francesco" , Terry Bowman , Joshua Hahn , Robert Richter , Subject: [PATCH v1 2/2] Documentation/driver-api/cxl: ACPI PRM Address Translation Support and AMD Zen5 enablement Date: Fri, 21 Nov 2025 13:16:51 +0100 Message-ID: <20251121121655.338491-2-rrichter@amd.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251121121655.338491-1-rrichter@amd.com> References: <20251121121655.338491-1-rrichter@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B36F:EE_|DS0PR12MB6559:EE_ X-MS-Office365-Filtering-Correlation-Id: 18987167-940e-424b-a733-08de28f7e9ef X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|82310400026|376014|36860700013|1800799024|13003099007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?N3NGRDJLS3BwcUxHd0tmYlc0Sk5tUHdzVHU0ZGZ5MjlmN3R2TWZMMElxR1pZ?= =?utf-8?B?YUNvWVJpUDdzdGc0ZHArTHIvQithbWJPMkhCNUU2aDFHcEViNk5sb1hWZk5j?= =?utf-8?B?NEM4azVhb29hRGVDYnhVTkRZVGhFMzNuUUh0QXlRaWtzMlFML2RVSVhNcTRU?= =?utf-8?B?bmpsZ2hvSHNFaFRQdllOSzh2SnFsT2xPZjNWK09VNm5BZFJIRnJaai9OVnBl?= =?utf-8?B?cGRxak5IUW43ZjJCcjJ6d0R0ZlhreHBWWmxTb3JKb1dETUtZKyttQ2M5TXVo?= =?utf-8?B?RzUySFZqd3p5dE5tSG9ad2tURDVqVVNGTGM3dFBmYkJWVll5UnZBVGpkUmdW?= =?utf-8?B?akkvVjVLendKWUFQSGVZbHF0OXFhRnhlVGVmNVljMzdjNU5HeWY1TTFCbjVa?= =?utf-8?B?SFowVFhJL2hvZ3ZwRU5RdUczL0Q3cE1HVTFENHRlN2RJa1RRT0RuWlFyUDZP?= =?utf-8?B?SmdNOGJERy85SHJzMHQxMm8zS2dwcW1xc1B4cFlCdE8zWlZ2M3dyYXUyTHdi?= =?utf-8?B?TW9rcmYveGh2dHV6U1FreTZHQ3VCZUZEdmdqdlV0eXhkWmRpalQvVDA5U2Ro?= =?utf-8?B?WFI4d0kxQWFveWI2aUxacTJydTZtdHRoT0ZXZUNTcEZiM3pWK2tQUEl3TDhu?= =?utf-8?B?Mk5jYXF1Wm02UkEyNjF0ZHo3UStlcXE4anAxekZMKzNyVWNwMXowbTB1MWtr?= =?utf-8?B?MGFaaWd0MzB5b2Nzd3BJY0ttTHBWU3JzVWdLdmxiTGtCTEtjQlpKZmU1Wm05?= =?utf-8?B?UWtEOHdOSThYQld2UEs0UmQwaXkySW1FZ3dPV1hqeHNIYk50Q0dVSlhyaFlP?= =?utf-8?B?VmFWc0YzMDZnajdOYjZuMTQza3R6ZkxZNWJpa2xLTzJFZTRtMnVzZnJrR1F6?= =?utf-8?B?QzA2bWQ1bUU1SCtUdDE4TWVQbENXTGQ3cityUm5qZjhsbkdTUmF3VFg4cklE?= =?utf-8?B?c3JYRWpIN0pvazloaVk3RkduMmFTZjFybVVNMzhrSnlRUGZVaDg4aGxpTTI3?= =?utf-8?B?QmNCdDJzdkhNZU5kaEVEVnBMbVMzenBmRVY0RGZTL2ZVOVVIODBQNXVUTkRD?= =?utf-8?B?TmlQOTRHOG5pbkVsVllid1FCNnphQkNUdThOSDQxZGRFVTBMTTB3V25hUXUw?= =?utf-8?B?N05oMG5DcVFHRnBNekhaNXRTblBmMXlqZlZ5M28wK2ZiTDlNRWxGOFd2eUhM?= =?utf-8?B?V2ptMlhrY2ZhaHZ1N1dMMFUwOC95Tm9UYVN6NGRBSVFNdHMvbTYwY0NQTlNm?= =?utf-8?B?QklKOXZhM3NxZ0hVZC9mNDNtU3llblZkVTRtcnFwYmcxbXlFNUw4d2Z4MWlT?= =?utf-8?B?MlNwUFJITzJ4clBDMzVlMWdvSlZURndPbm1JWWdha0ladCsrSWV2aFJVTHBz?= =?utf-8?B?YWRjN3VaNkhNZmZnaTZNNzZaWC9EM0dEZjNpV1ZlZmIzQ0VJL0E4YUZTbXdW?= =?utf-8?B?RlRHaExob2NPV0xPMWNOQ1h4a1Z2bVFFUEVXMzhLam95dm9PQ0F4YTdYWFZG?= =?utf-8?B?YWdkQmllc2NFVTdlQ3VXVXZ3d1VYbjh3MStEb3B2UEd1TVlteURaQ0FaYWRj?= =?utf-8?B?K1Y2b3BEa1dkcUJIWFN5NzI4ZThFWmtrR0hLUmZFYk9GZ2NreDZkTWFwQXVS?= =?utf-8?B?MlhwNTRycEdDUHNhV3RVMktsWjRYU1RTQjREQ0RjU0dKeDloVS8rNnZUQ0c0?= =?utf-8?B?YW50UEFLNGtWSDRyOFhlZnhvQzBoT0YySkRaV0FUVklBelRKRXg5YmdKK0JB?= =?utf-8?B?OVh3NnM2bHRIS2VsaHFrZ0M4amNwWm81TGFzU0ZZMnE3S0ZweWxINXNYeFBs?= =?utf-8?B?QzJXRlduUUI5VnQ2aWI2NEVPaEIzajNkREErTisvUktJUG1PeHhxc2lCUCtX?= =?utf-8?B?cDQrczg3eS9NZEFONWFDRWpzR1JCc2lweHNjNVJYOHN5cHluZFZkOFVIbjln?= =?utf-8?B?S0ZIczcrL2RSRnBDVU5qYkk4K3FHWUxPcFUyY2RmNXQ4eWF4b3hnTnpxTVQ3?= =?utf-8?B?QWl3cFU3L3g1NjJMWlhLdzFJcHN2UkxkVHJzZ0ZNbS9VUnh6MGxHaW5FZ3kw?= =?utf-8?Q?L6x1tz?= 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)(7416014)(82310400026)(376014)(36860700013)(1800799024)(13003099007);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Nov 2025 12:17:17.9597 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 18987167-940e-424b-a733-08de28f7e9ef 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: BN3PEPF0000B36F.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB6559 This adds a convetion document for the following patch series: [v7,00/11] cxl: ACPI PRM Address Translation Support and AMD Zen5 enablement https://patchwork.kernel.org/project/cxl/cover/20251114213931.30754-1-rrichter@amd.com/ Signed-off-by: Robert Richter --- Documentation/driver-api/cxl/conventions.rst | 1 + .../driver-api/cxl/conventions/cxl-atl.rst | 175 ++++++++++++++++++ 2 files changed, 176 insertions(+) create mode 100644 Documentation/driver-api/cxl/conventions/cxl-atl.rst diff --git a/Documentation/driver-api/cxl/conventions.rst b/Documentation/driver-api/cxl/conventions.rst index 53f31a229c8d..cf427afac58b 100644 --- a/Documentation/driver-api/cxl/conventions.rst +++ b/Documentation/driver-api/cxl/conventions.rst @@ -8,4 +8,5 @@ Compute Express Link: Linux Conventions :caption: Contents conventions/cxl-lmh.rst + conventions/cxl-atl.rst conventions/template.rst diff --git a/Documentation/driver-api/cxl/conventions/cxl-atl.rst b/Documentation/driver-api/cxl/conventions/cxl-atl.rst new file mode 100644 index 000000000000..9c14856e1782 --- /dev/null +++ b/Documentation/driver-api/cxl/conventions/cxl-atl.rst @@ -0,0 +1,175 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: + +ACPI PRM CXL Address Translation +================================ + +Document +-------- + +CXL Revision 3.2, Version 1.0 + +License +------- + +SPDX-License Identifier: CC-BY-4.0 + +Creator/Contributors +-------------------- + +- Robert Richter, AMD + +Summary of the Change +--------------------- + +The CXL Fixed Memory Window Structure (CFMWS) describes zero or more +Host Physical Address (HPA) windows that are associated with each CXL +Host Bridge. The HPA ranges of an CFMWS may include addresses that are +currently assigned to CXL.mem devices, or an OS may assign ranges from +an address window to a device. + +Host-managed Device Memory is Device-attached memory that is mapped to +system coherent address space and accessible to the Host using +standard write-back semantics. The managed address range is configured +in the CXL HDM Decoder registers of the device. An HDM Decoder in a +device is responsible for converting HPA into DPA by stripping off +specific address bits. + +CXL devices and CXL bridges use the same HPA space. It is common +across all components that belong to the same host domain. The view of +the address region must be consistent on the CXL.mem path between the +Host and the Device. + +This is described in the current CXL specification (Table 1-1, 3.3.1, +8.2.4.20, 9.13.1, 9.18.1.3). [#cxl-spec-3.2]_ + +Depending on the interconnect architecture of the platform, components +attached to a host may not share the same host physical address space. +Those platforms need address translation to convert an HPA between the +host and the attached component, such as a CXL device. The translation +mechanism is host-specific and implementation dependent. + +E.g., x86 AMD platforms use a Data Fabric that manages access to +physical memory. Devices have an own memory space and can be +configured to use 'Normalized addresses' different to System Physical +Addresses (SPA). Address translation is needed then. Details are +described also under x86 AMD +Documentation/admin-guide/RAS/address-translation.rst. + +Those AMD platforms provide PRM handlers in firmware to perform +various types of address translation, including for CXL endpoints. +AMD Zen5 systems implement the ACPI PRM CXL Address Translation +firmware call. The ACPI PRM handler has a specific GUID to uniquely +identify platforms with support of Normalized addressing. This is +documented in the ACPI v6.5 Porting Guide, Address Translation - CXL +DPA to System Physical Address. [#amd-ppr-58088]_ + +When in Normalized address mode, HDM decoder address ranges must be +configured and handled differently. Hardware addresses used in the HDM +decoder configurations of an endpoint are not SPA and need to be +translated from the endpoint's to its CXL host bridge's address range. +This is esp. important to find an endpoint's associated CXL Host +Bridge and HPA window described in the CFMWS. Also, the interleave +decoding is done by the Data Fabric and the endpoint does not perform +decoding when converting HPA to DPA. Instead, interleaving is switched +off for the endpoint (1 way). Finally, address translation might also +be needed to inspect the Endpoint's hardware addresses, such as during +profiling, tracing or error handling. + +For example, with Normalized addressing the HDM decoders could look as +following: + +.. code-block:: none + + /sys/bus/cxl/devices/endpoint5/decoder5.0/interleave_granularity:256 + /sys/bus/cxl/devices/endpoint5/decoder5.0/interleave_ways:1 + /sys/bus/cxl/devices/endpoint5/decoder5.0/size:0x2000000000 + /sys/bus/cxl/devices/endpoint5/decoder5.0/start:0x0 + /sys/bus/cxl/devices/endpoint8/decoder8.0/interleave_granularity:256 + /sys/bus/cxl/devices/endpoint8/decoder8.0/interleave_ways:1 + /sys/bus/cxl/devices/endpoint8/decoder8.0/size:0x2000000000 + /sys/bus/cxl/devices/endpoint8/decoder8.0/start:0x0 + /sys/bus/cxl/devices/endpoint11/decoder11.0/interleave_granularity:256 + /sys/bus/cxl/devices/endpoint11/decoder11.0/interleave_ways:1 + /sys/bus/cxl/devices/endpoint11/decoder11.0/size:0x2000000000 + /sys/bus/cxl/devices/endpoint11/decoder11.0/start:0x0 + /sys/bus/cxl/devices/endpoint13/decoder13.0/interleave_granularity:256 + /sys/bus/cxl/devices/endpoint13/decoder13.0/interleave_ways:1 + /sys/bus/cxl/devices/endpoint13/decoder13.0/size:0x2000000000 + /sys/bus/cxl/devices/endpoint13/decoder13.0/start:0x0 + +Note the endpoint interleaving configurations with a direct mapping +(1-way). + +With PRM calls, the kernel can determine the following mappings: + +.. code-block:: none + + cxl decoder5.0: address mapping found for 0000:e2:00.0 (hpa -> spa): + 0x0+0x2000000000 -> 0x850000000+0x8000000000 ways:4 granularity:256 + cxl decoder8.0: address mapping found for 0000:e3:00.0 (hpa -> spa): + 0x0+0x2000000000 -> 0x850000000+0x8000000000 ways:4 granularity:256 + cxl decoder11.0: address mapping found for 0000:e4:00.0 (hpa -> spa): + 0x0+0x2000000000 -> 0x850000000+0x8000000000 ways:4 granularity:256 + cxl decoder13.0: address mapping found for 0000:e1:00.0 (hpa -> spa): + 0x0+0x2000000000 -> 0x850000000+0x8000000000 ways:4 granularity:256 + +The corresponding CXL host bridge (HDM) decoders and root decoder +(CFMWS) show and match with the calculated endpoint mappings: + +.. code-block:: none + + /sys/bus/cxl/devices/port1/decoder1.0/interleave_granularity:256 + /sys/bus/cxl/devices/port1/decoder1.0/interleave_ways:4 + /sys/bus/cxl/devices/port1/decoder1.0/size:0x8000000000 + /sys/bus/cxl/devices/port1/decoder1.0/start:0x850000000 + /sys/bus/cxl/devices/port1/decoder1.0/target_list:0,1,2,3 + /sys/bus/cxl/devices/port1/decoder1.0/target_type:expander + /sys/bus/cxl/devices/root0/decoder0.0/interleave_granularity:256 + /sys/bus/cxl/devices/root0/decoder0.0/interleave_ways:1 + /sys/bus/cxl/devices/root0/decoder0.0/size:0x8000000000 + /sys/bus/cxl/devices/root0/decoder0.0/start:0x850000000 + /sys/bus/cxl/devices/root0/decoder0.0/target_list:7 + +The following changes of the specification are needed: + +* Allow a CXL device to be in a different HPA space other than the + host's space. + +* The platform can use implementation-specific address translation + when crossing memory domains on the CXL.mem path between the Host + and the Device. + +* The kernel (OSPM) determines Endpoint SPA range and interleaving + configuration using platform specific address translation methods. + +Benefits of the Change +---------------------- + +Without the change, the OSPM may not determine the memory region and +Root Decoder of an Endpoint and its corresponding HDM decoder. Region +creation would fail. Platforms with a different interconnect +architecture would fail to setup and use CXL. + +References +---------- + +.. [#cxl-spec-3.2] Compute Express Link Specification, Revision 3.2, Version 1.0, + https://www.computeexpresslink.org/ + +.. [#amd-ppr-58088] AMD Family 1Ah Models 00h–0Fh and Models 10h–1Fh, + ACPI v6.5 Porting Guide, Publication # 58088, + https://www.amd.com/en/search/documentation/hub.html + +Detailed Description of the Change +---------------------------------- + +Add the following paragraph in 8.2.4.20 CXL HDM Decoder Capability +Structure of the specification [#cxl-spec-3.2]_ to the end: + +"A device may use a different HPA space that is not common to other +components of the host domain. The platform is responsible for address +translation when crossing HPA spaces. The OSPM must determine the +interleaving configuration and perform address translation to HPA +ranges of the HDM decoders as needed. The translation mechanism is +host-specific and implementation dependent." -- 2.47.3