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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Nov 2025 08:50:40.8408 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d28416f0-5eae-4335-2efc-08de235ae3d0 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000EE36.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB4054 On 11-11-2025 20:45, Sean Christopherson wrote: > On Tue, Nov 11, 2025, Shivansh Dhiman wrote: >> On 17-08-2024 05:43, Sean Christopherson wrote: >>> On Thu, Aug 08, 2024, Ravi Bangoria wrote: ... > >> =========================================================== >> Issue 1: Interception still enabled after enabling LBRV >> =========================================================== >> Using the 6.16 upstream kernel (unpatched) I ran the KUT tests and they passed >> when run from both the bare metal and from inside a L1 guest. However for L2 >> guest, when looking at the logs I found that RDMSR interception of LBR MSRs is >> still enabled despite the LBRV is enabled for the L2 guest. Effectively, the >> reads are emulated instead of being virtualized, which is not the intended >> behaviour. KUT cannot distinguish between emulated and virtualized RDMSR, and >> hence the test passes regardless. > > I haven't looked closely at your patch or at Yosry's patches, but I suspect this > was _just_ fixed: > > https://lore.kernel.org/all/20251108004524.1600006-1-yosry.ahmed@linux.dev Thanks Sean. I tested Yosry's patches and they indeed have solved this issue. > >> =========================================================== >> Issue 2: Basic LBR KUT fails with Sean's implementation >> =========================================================== >> After using your implementation, all KUTs passed on the bare metal. With LBRV >> enabled for L2, RDMSR interception of LBR MSRs is disabled as intended. >> However, when running KUT tests inside an L1 guest, the tests fail. > > Same story here: I haven't had cycles to actually look at code, but Yosry also > posted a pile of changes for KUT: > > https://lore.kernel.org/all/20251110232642.633672-1-yosry.ahmed@linux.dev This issue was also related to buggy LBRV in the kernel. Yosry's patches have fixed this issue as well and I've verified it. There was a slight flakiness in the KUT which was later fixed by another patch by Yosry's. [1] Thanks, Shivansh 1. https://lore.kernel.org/all/20251113224639.2916783-1-yosry.ahmed@linux.dev/