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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?7XnB8Z/HekyTb+rI8uU9cgVz/0UKv9JorNssFZhWolanwYMUyoLMkJ9PgxN3?= =?us-ascii?Q?j1WbAm4cjw6vtV+fB2x3XbT0cmr6MjHruu+XQfyQHtOMeZ7TM7WOTQV110rn?= =?us-ascii?Q?PhjDJxDaHLyul7qKk7jsWL+QR1SUQrJEdPq4V3xtbIQzchu1skm1f1ljLF5a?= =?us-ascii?Q?5qALv3V5qv2mUZiwMrJ0lg4mnmW6xW6vG6Emt9LiYXDh1sK/aFrh2hFJ/1w/?= =?us-ascii?Q?qSM+IQahhirlM6MJd3slsQDDK0xmgK4jh7vlJhT/4slsJggBnJlMz0K7HZK0?= =?us-ascii?Q?RmaSjV6BWda+T6QH4bvIgHblQOjB7mkYDzPmU4tvX14OcHpVBQuiZZJwQ1ft?= =?us-ascii?Q?GuOpfp3IqaBn/8Uq/eWQvFDZ430NF00fz6JEZ8qX/G1+FRioNySFOCRGt0GM?= =?us-ascii?Q?+/Zdy9/lBy+qSMAH9RAlNRQilFwTVKO1sklImW63miSdy0hW05qiokW/Bo2N?= =?us-ascii?Q?nQ0Wi0DL+qUqsJqkYxs6xVOhVI8W4Tmat44MAunR6hY1Mj0w39CTIAi+9ORV?= =?us-ascii?Q?LONdHjk1Qjh+gkNDTXI4rzJ4saV6IsQp5tNl2Bs2ewzSJLzWLJuTk4Q/KL3a?= =?us-ascii?Q?J+o9i4QYoPb2kd0seuOEIBsit+/1NDOzGhllZSMfOeGwjbR3nxjmz7LH4tsV?= =?us-ascii?Q?KWZV+Tkz7Bzwjn+GWUH11QzLc7Jei6voGq/FG1/eRRylm+yP07/VVYMAIft+?= =?us-ascii?Q?DrG/d+mmsbehJe4kDmvWezZFroMladMrZf7O0sEyLDn+HMezRc2yenkLYl9+?= =?us-ascii?Q?A3aRLgswuvEhM5sG937XboLdneh8QjQveaTiBOREl0I5pEK1dfR8ywQlMQHm?= =?us-ascii?Q?ljlOuOy6iSjxigGzsTihsLjKOyJkL2A7OZ7PyFCe1TCJMCvgjoz+unsRjkRf?= =?us-ascii?Q?TF3EC0Uvvgq14o23WYKq9ELLDsCpY0BsJJhM5kurx9YT1jZPScLcVlfR5nrx?= =?us-ascii?Q?eE/cdoWdyhJV2GE4lGppqjJyGnwhQJ5LEf7FewzYq23xNriGhoGQ1f5qc5TK?= =?us-ascii?Q?RPueA2fUqIuvx8tD7pqEhxTF5qrqycnhjE5pWrh4fU2feFEZ66f2L2KzcMyB?= =?us-ascii?Q?isExfNGJCjH6qRHOfdkhSlbe3lcK8UdDT9A7lTygQyqFR5Sq7Y/yDaW/LzaM?= =?us-ascii?Q?FaZi7glw+ZRw21fa3Ki6XAWJbxT+ntC2WYZ1KL4Z5y1fEdJtbNh4AmoFUY3p?= =?us-ascii?Q?SpcTUoG6xukXW68ncweIlZIFe0FOZ60QGw8+AQNIurtJClrB0i7GxEslFs7a?= =?us-ascii?Q?bKvcxln5p7kuZ6xzzPurJODqsVSLVnw8+FQhq++GLg+nfjhDVod7Uuspcmgs?= =?us-ascii?Q?1thkGC1xZltSPdst7Oi19VPgN1XVq9elGqYIiX4kST1k10fLom9p/cdRNKNO?= =?us-ascii?Q?+RD4+PSsHb6WPGBAd+wJTQWgpSnx5BvPpQfonrZu83wAn8P/J7sQo+VK/mNp?= =?us-ascii?Q?SX3dA2BJhJtKWdLskYegE/dRxVpHlvWaDUGvh9B+2H2ZE5juL+nuMkzpn6jt?= =?us-ascii?Q?uOkiGu4+dJ4nDa6fDT7HJfQjlQM970qLIk4kcEaZAtdv0OCVxk3zRP3w3RH1?= =?us-ascii?Q?HfBGPQhZ13LptzRgl7SK3UdIbQL049aae1URL2oc?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8db6dfd5-0b7e-4b1f-2363-08ddf5529bc5 X-MS-Exchange-CrossTenant-AuthSource: BL1PR12MB5995.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Sep 2025 18:55:30.7977 (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: 8jgLAZIbPrBAhHzZB7kuKnUqf2WjAHJASZ2/ZsT/Vq1jIqY/9CPYsAlnwZzKlXnm/SV31XFtKg5tkKXchgfwwQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB8768 On Fri, Sep 12, 2025 at 04:23:07PM -0700, Sean Christopherson wrote: > Synchronize XSS from the GHCB to KVM's internal tracking if the guest > marks XSS as valid on a #VMGEXIT. Like XCR0, KVM needs an up-to-date copy > of XSS in order to compute the required XSTATE size when emulating > CPUID.0xD.0x1 for the guest. > > Treat the incoming XSS change as an emulated write, i.e. validatate the > guest-provided value, to avoid letting the guest load garbage into KVM's > tracking. Simply ignore bad values, as either the guest managed to get an > unsupported value into hardware, or the guest is misbehaving and providing > pure garbage. In either case, KVM can't fix the broken guest. > > Note, emulating the change as an MSR write also takes care of side effects, > e.g. marking dynamic CPUID bits as dirty. > > Suggested-by: John Allen > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/svm/sev.c | 3 +++ > arch/x86/kvm/svm/svm.h | 1 + > 2 files changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 0cd77a87dd84..0cd32df7b9b6 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -3306,6 +3306,9 @@ static void sev_es_sync_from_ghcb(struct vcpu_svm *svm) > if (kvm_ghcb_xcr0_is_valid(svm)) > __kvm_set_xcr(vcpu, 0, kvm_ghcb_get_xcr0(ghcb)); > > + if (kvm_ghcb_xss_is_valid(svm)) > + __kvm_emulate_msr_write(vcpu, MSR_IA32_XSS, kvm_ghcb_get_xss(ghcb)); > + It looks like this is the change that caused the selftest regression with sev-es. It's not yet clear to me what the problem is though. Thanks, John