> + /* > + * As a first step, a guest could only enable LBR feature if its cpu > + * model is the same as the host because the LBR registers would > + * be pass-through to the guest and they're model specific. > + */ > + if (boot_cpu_data.x86_model != guest_cpuid_model(vcpu)) > + return false; Could we relax this in a followon patch? (after this series is merged) It's enough of the perf cap LBR version matches, don't need full model number match. This would require a way to configure the LBR version from qemu. This would allow more flexibility, for example migration from Icelake to Skylake and vice versa. -Andi
