On 09/10/19 03:42, Yang Weijiang wrote: > + if (guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && > + boot_cpu_has(X86_FEATURE_XSAVES)) > + guest_cpuid_set(vcpu, X86_FEATURE_XSAVES); > + This is incorrect, as it would cause a change in the guest ABI when migrating from an XSAVES-enabled processor to one that doesn't have it. As long as IA32_XSS is 0, XSAVES is indistinguishable from XSAVEC, so it's okay if the guest "tries" to run it despite the bit being clear in CPUID. Paolo
