Re: [PATCH v2 06/29] LoongArch: KVM: Implement vcpu create and destroy interface

[Paolo Bonzini]

On 2/22/23 02:52, Tianrui Zhao wrote:
> > > +    vcpu->arch.guest_eentry = (unsigned long)kvm_context->kvm_eentry;
> > > +    vcpu->arch.vcpu_run = kvm_context->kvm_enter_guest;
> > > +    vcpu->arch.handle_exit = _kvm_handle_exit;
> >
> > Here as well, whatever is constant must not be stored in struct 
> > kvm_arch_vcpu.
> >
> > Paolo
>
> Thanks,  we use this in vcpu_arch because the vcpu_arch is used as 
> argument in switch.S' methods, we can quickly access the guest_eentry 
> and handle_exit by using the  KVM_ARCH_GEENTRY, KVM_ARCH_HANDLE_EXIT 
> offsets. If we change to global variable ,  we should relocate it in 
> switch.S and may lead  to lower accessing speed.

For guest_eentry and handle_exit this is correct so you can add a 
comment in kvm_host.h, like

	/* Pointers stored here for easy access from assembly code.  */

However, vcpu->arch.vcpu_run is not used in switch.S so there is no need 
to store it in struct kvm_arch_vcpu.  Since you're already going to move 
kvm_enter_guest out of kvm_context and into a global variable, please 
give it the right pointer-to-function type instead of using unsigned long.

Paolo