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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ZBXfNGqSuTmfest4QJfhjD2OtUOkQsXVel4afZAD4e6wKlFR/hG2H5sJzs09?= =?us-ascii?Q?Y4aVjyLdHxqEtibg3noCwDYBtXCEvpo6V7B7n6R3uCzh2eK1rsNvCpI4Vqi6?= =?us-ascii?Q?1SKLAaZ2WzZcukIindl+sxcDRB/PEbzm/i10BI9r6WLKBK2jMtgU1KGarpZK?= =?us-ascii?Q?lYTi0x82nG52sSo2HCF5gHVg5hDKwOx05Ac1vtxxLgRkGDYmaWVCwZXUao/5?= =?us-ascii?Q?MV2mH74fT4exxBBiYDFa+2HqGt9w0+0I1V+pD49nvCiFNWLuJOYJgehQZVVF?= =?us-ascii?Q?lhOul1rgyWkcxN/tuNd2gOmEpzVfhDmRpabU5gl1F+vs3XgeSSwIF+gmgIhj?= =?us-ascii?Q?iteU+pn8B3Jo5mVog27uf7Mpd8kZ5KWZ1kpBeTCy24aTOEF4Osve9wlI9eKp?= =?us-ascii?Q?CZRXi2UbusbMnNjKoslC+UGtLvkgHNJzeeZ+iv/CtLEadi+5m1rrPerN0anz?= =?us-ascii?Q?NkuaYROkMVWIFdkLRadWHp38G+ZH+BFjbie8JTAgIapB00L1MkwxVF06mv/L?= =?us-ascii?Q?aS4pTEifwIwI6OcdMWVIjA8xTV3w/Z/aCWJlIl4qv8qukwqBjLTsbilkn+Xa?= =?us-ascii?Q?oyCtCwGWp+dv+U4Um3JWxtlUWY+dmn/20+zgnj8i8c860Gqtpc/3K12hX/m+?= =?us-ascii?Q?sXuWAbznnxLohoh6W5Xeep2/T7E0wycwT7/rLM28CzOS/fqZtzDZrcPFmGWO?= =?us-ascii?Q?B6/Zi3xEZau3Cvu77c+xCC68KR5WN7wddoc7SWRMNhZT1HCbqe9G1+3fp7Xy?= =?us-ascii?Q?FAW+uVIXMZJ4g6+zNQlJuARD13r9ruWXqmWs+tV5DhQA9aBod9CbcQ8kdW/5?= =?us-ascii?Q?/ooLZGldIA2eyoCTUQ1UtWmfYuA8ZXSeIvzNijo0+BMgZfdQ+wwkLH3FUwQQ?= =?us-ascii?Q?Oj2MezXKhLopqGvcSLQwIUh241NUmMPNu+N8yAuvuwM0gNmxIB8UzpUd8YlR?= =?us-ascii?Q?3gG3V+bmrJMpLtIg9yJK1E3VRMeJIikm16H3K8U8YC7EkDwDWNEagq8dH6W+?= =?us-ascii?Q?pJygAgoYYwv+58e1M203uJVjAX96wfmih7CBLoejLgT/76Zy9nfWFMjfbFwk?= =?us-ascii?Q?P2wJpG/tFz/svntb+gtpch4TJMEFwK9YAbbq0281G5swPuxlMn96EVR/4akK?= =?us-ascii?Q?o2CmAqJpIuNPJcIgClDHlUAFHb2VRRw0eaau9MHNnFOgV0Bz8PfQNWxJFH82?= =?us-ascii?Q?HU4ETO0mMn+37NSa+WI+fFAX+JkeNKGsL4RmakrwFDzRPBA57GGJ6sia1KvS?= =?us-ascii?Q?LrLH2CKAk7GgBh9HP8ijEfFGGT2fD3riZOtNDqaObaBmjx1TgZroQgpRNKKx?= =?us-ascii?Q?KXhQxwSMjSCZClZ3IfX2IkSHhQlzfwuVDxMbkqcfCexd8mKrC3o3SyCEPsN4?= =?us-ascii?Q?TWqKkIV9mtyAjA6UcA/NQ4KwvZ/oX2nuhcVpJUjvxfwHMd8/YgSBfzF+9RKs?= =?us-ascii?Q?Ixzy0Hdg/gM8Oc0bjOjGTFIl87qEw2zbWbbXzQ0SHjd3ccyEjAhIMvPfquPZ?= =?us-ascii?Q?/kfPs4mQv2hbzfHDqpzlG2egHgyitULH5aaUIEEcnHDGR5x0g7xAwLbu0dXs?= =?us-ascii?Q?O0fyFxdJo0/uTucPBN/3m0uP2c1kT52rMFKBXriz?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 90ff213a-c8b6-4558-d4a0-08de10a7096f X-MS-Exchange-CrossTenant-AuthSource: DM4PR12MB6373.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Oct 2025 13:37:53.9392 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: CKtsCEvABr0Df/oHzq0iali/oSQ8ZqJeHMsiR6KvG7FxtxUltsxMYvalfwL0pXO6UrCSRablkBGSaA29852EQw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB6873 On Tue, Oct 21, 2025 at 02:29:09PM +0200, Borislav Petkov wrote: > On Tue, Sep 30, 2025 at 04:45:45PM +0000, Yazen Ghannam wrote: > > Recent AMD node rework removed the "search and count" method of caching > > AMD root devices. This depended on the value from a Data Fabric register > > that was expected to hold the PCI bus of one of the root devices > > attached to that fabric. > > > > However, this expectation is incorrect. The register, when read from PCI > > config space, returns the bitwise-OR of the buses of all attached root > > devices. > > > > This behavior is benign on AMD reference design boards, since the bus > > numbers are aligned. This results in a bitwise-OR value matching one of > > the buses. For example, 0x00 | 0x40 | 0xA0 | 0xE0 = 0xE0. > > > > This behavior breaks on boards where the bus numbers are not exactly > > aligned. For example, 0x00 | 0x07 | 0xE0 | 0x15 = 0x1F. > > Do I see it correctly that one of the root device's PCI bus is always 0x0 so > you can simply read that one and you can keep the current code? > It's correct that one of the root devices will be on bus 0x0. But that device will be part of AMD node 0. So we still need to pick a root device for the other, if any, AMD nodes in the system. For example, a system with 2 AMD nodes could have this: Node 0 : 0x00 0x07 0x0e 0x15 Node 1 : 0x1c 0x23 0x2a 0x31 Thanks, Yazen