Re: [PATCH 1/2] x86,kvm: move qemu/guest FPU switching out to vcpu_run

[Quan Xu]

On 2017-11-17 01:50, Paolo Bonzini wrote:
> On 16/11/2017 15:28, Quan Xu wrote:
> >   	vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> >   
> > + kvm_load_guest_fpu(vcpu);
> > +
> >   	for (;;) {
> >   		if (kvm_vcpu_running(vcpu)) {
> >   			r = vcpu_enter_guest(vcpu);
> >
> > <<
> >
> >
> >
> >   as Rik dropped kvm_load_guest_fpu(vcpu) in vcpu_enter_guest() ..
> >  Â in case still in kvm mode, how to make sure to pkru is always the
> > right one before enter guest mode, not be preempted before
> > preempt_disable()Â after migration? :(
> As you know:
>
> 1) kvm_load_guest_fpu doesn't load the guest PKRU, it keeps the
> userspace PKRU.
>
> 2) the guest PKRU is only ever set in a preemption-disabled area
>
> Thus, context switch always sees the userspace PKRU.  The guest PKRU is
> only set the next time vmx_vcpu_run executes.
>
> Paolo

Paolo, thanks for your explanation!!:-)
Rik, could you cc me in v2?

Quan