Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 1/12/22 14:58, Vitaly Kuznetsov wrote: >> - best = kvm_find_cpuid_entry(vcpu, 0xD, 1); >> + best = cpuid_entry2_find(entries, nent, 0xD, 1); >> if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) || >> cpuid_entry_has(best, X86_FEATURE_XSAVEC))) >> best->ebx = xstate_required_size(vcpu->arch.xcr0, true); >> >> - best = kvm_find_kvm_cpuid_features(vcpu); >> + best = __kvm_find_kvm_cpuid_features(vcpu, vcpu->arch.cpuid_entries, >> + vcpu->arch.cpuid_nent); >> if (kvm_hlt_in_guest(vcpu->kvm) && best && > > I think this should be __kvm_find_kvm_cpuid_features(vcpu, entries, nent). > Of course. >> >> + case 0x1: >> + /* Only initial LAPIC id is allowed to change */ >> + if (e->eax ^ best->eax || ((e->ebx ^ best->ebx) >> 24) || >> + e->ecx ^ best->ecx || e->edx ^ best->edx) >> + return -EINVAL; >> + break; > > This XOR is a bit weird. In addition the EBX test is checking the wrong > bits (it checks whether 31:24 change and ignores changes to 23:0). Indeed, however, I've tested CPU hotplug with QEMU trying different CPUs in random order and surprisingly othing blew up, feels like QEMU was smart enough to re-use the right fd) > > You can write just "(e->ebx & ~0xff000000u) != (best->ebx ~0xff000000u)". > >> >> + default: >> + if (e->eax ^ best->eax || e->ebx ^ best->ebx || >> + e->ecx ^ best->ecx || e->edx ^ best->edx) >> + return -EINVAL; > > This one even more so. Thanks for the early review, I'm going to prepare a selftest and send this out. -- Vitaly
