On Wed, Oct 3, 2018 at 1:29 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > On 01/10/2018 23:25, Sean Christopherson wrote: >> kvm-intel.flexpriority is a >> haphazard param that is inconsistently honored by KVM, e.g. it still >> controls VIRTUALIZE_APIC_ACCESSES but not TPR_SHADOW, CR8-exiting or >> VIRTUALIZE_X2APIC_MODE > > This is on purpose: the original purpose of VIRTUALIZE_APIC_ACCESSES was > to speed up Windows XP and 2003, which didn't use CR8. Processors > without it could already execute newer Windows versions without the > overhead of emulating TPR accesses (notice how VIRTUALIZE_APIC_ACCESSES > is a secondary execution control, while TPR_SHADOW is a primary control). If the setting is only for specific guests, why is it a kernel parameter rather than a per-VM capability?
