Re: Seeking a KVM benchmark

[Paolo Bonzini <pbonzini@redhat.com>]

> Assuming you're running both of my patches (LOAD_EFER regardless of
> nx, but skip LOAD_EFER of guest == host), then some of the speedup may
> be just less code running.  I haven't figured out exactly when
> vmx_save_host_state runs, but my patches avoid a call to
> kvm_set_shared_msr, which is worth a few cycles.

Yes, that's possible.  vmx_save_host_state is here:

        preempt_disable();

        kvm_x86_ops->prepare_guest_switch(vcpu);  // <<<<
        if (vcpu->fpu_active)
                kvm_load_guest_fpu(vcpu);
        kvm_load_guest_xcr0(vcpu);

        vcpu->mode = IN_GUEST_MODE;

        srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);

and it's a fairly hot function.

Paolo