Re: [PATCH v21 05/23] KVM: arm64: Track the type of VM in kvm_arch

[Suzuki K Poulose]

On 02/10/2026 16:40, Marc Zyngier wrote:
> On Fri, 02 Oct 2026 16:15:07 +0100,
> Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > > index 0f4e8b71fa85d..9ba86450fe4af 100644
> > > --- a/arch/arm64/kvm/mmu.c
> > > +++ b/arch/arm64/kvm/mmu.c
> > > @@ -2624,7 +2624,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
> > >    	hva_t hva, reg_end;
> > >    	int ret = 0;
> > >    -	if (kvm_vm_is_protected_pkvm(kvm)) {
> > > +	if (kvm_vm_is_protected(kvm)) {
> >
> > We have slightly different handling for Realms. The final code for this
> > looks like :
> >
> > 	if (kvm_vm_is_protected(kvm)) {
> > 		if (new &&
> > 		    new->flags & (KVM_MEM_LOG_DIRTY_PAGES | KVM_MEM_READONLY)) {
> > 			return -EPERM;
> > 		}
> > 	}
> >
> > 	if (kvm_vm_is_protected_pkvm(kvm)) {
> > 		/* Cannot modify memslots once a pVM has run. */
> > 		if (pkvm_hyp_vm_is_created(kvm) &&
> > 		    (change == KVM_MR_DELETE || change == KVM_MR_MOVE)) {
> > 			return -EPERM;
> > 		}
> > 	} else if (kvm_realm_is_created(kvm)) {
> > 		/*
> > 		 * Once the Realm is created, we cannot modify any slots that
> > 		 * could be providing private memory. i.e., guest_memfd backed
> > 		 * slots.
> > 		 * TODO: Handle trusted device private memory slots
> > 		 */
> > 		if (kvm_slot_has_gmem(old) || kvm_slot_has_gmem(new))
> > 			return -EPERM;
> > 	}
> >
> >
> > Of course we could invert the checks to detect vm_is_protected_pkvm()
>
> This is how I expect this stuff to be written.
>
> 	if (kvm_vm_is_protected(kvm) && new &&
> 	    new->flags & (KVM_MEM_LOG_DIRTY_PAGES | KVM_MEM_READONLY))
> 		return -EPERM;
>
> 	switch (kvm->vm_flavor) {
> 	case VM_PROTECTED_PKVM:
> 		/* Cannot modify memslots once a pVM has run. */
> 		if (pkvm_hyp_vm_is_created(kvm) &&
> 		    (change == KVM_MR_DELETE || change == KVM_MR_MOVE)) {
> 			return -EPERM;
> 		break;
> 	case VM_CCA:
> 		/*
> 		 * Once the Realm is created, we cannot modify any slots that
> 		 * could be providing private memory. i.e., guest_memfd backed
> 		 * slots.
> 		 * TODO: Handle trusted device private memory slots
> 		 */
> 		if (kvm_realm_is_created(kvm) &&
> 		    (kvm_slot_has_gmem(old) || kvm_slot_has_gmem(new)))
> 			return -EPERM;
> 		break;
> 	default:
> 		break;
> 	}

Yep, we can do that.

Cheers
Suzuki


> We have an enumeration. Make use of it. And the whole "is_created"
> crap needs to be sorted one way or another.
>
> 	M.