Re: [PATCH v12 06/11] KVM: vmx/pmu: Expose LBR to guest via MSR_IA32_PERF_CAPABILITIES

[Andi Kleen]

> +	/*
> +	 * 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