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

[Marc Zyngier <maz@kernel.org>]

On Fri, 02 Oct 2026 14:05:17 +0100,
Fuad Tabba <tabba@google.com> wrote:
> 
> Hi Marc,
> 
> On Fri, 02 Oct 2026 13:57:11 +0100, Marc Zyngier <maz@kernel.org> wrote:
> [...]
> > Just to make sure. Is that what you had in mind?
> 
> A diff is worth a thousand words :) Yes, that's it. With that, every
> remaining hyp user of vcpu_is_protected() only runs with pKVM, so the
> kern_hyp_va() case in the macro can go too.

Actually, scratch all of that. The whole thing is written upside down,
and makes little sense. I wish I had looked at it more closely...

The *_protected__pkvm() shouldn't exist at all, because nVHE is the
only context where it matters, and therefore we can specialise the
*normal* accessors for the nVHE context (see below). No *_pkvm(), no
kern_hyp_va(), nothing at all.

I'm also dead against the unprotected_pkvm() stuff, as it looks
pointlessly specialised. Specifically, this nugget is making my head
spin:

+       if (!kvm_vm_is_unprotected_pkvm(vcpu->kvm))
                return;

Honestly, we introduce the flavor stuff to make it easy to match
things on a particular VM type in a readable way. So why isn't this
reading:

	if (vcpu->kvm->arch.vm_flavor != VM_PROTECTED_PKVM)
		return;

which makes it pretty explicit. You can gate it with a
is_protected_kvm_enabled() if you want, as it was before.

	M.


diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 9e1fa00d96f7c..6b64f9610f3a3 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1519,41 +1519,22 @@ struct kvm *kvm_arch_alloc_vm(void);
 
 #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
 
-#define kvm_vm_is_protected(kvm)	((kvm)->arch.vm_flavor >= __VM_PROTECTED)
-/*
- * Accessing vcpu->kvm from nVHE hyp stub is tricky, as we need to convert the
- * pointer to the hyp VA. With pKVM, the nVHE code runs with the hyp_vcpu,
- * which is populated correctly.
- */
-#define vcpu_is_protected(vcpu)						\
-	({								\
-		struct kvm *__kvm = READ_ONCE((vcpu)->kvm);		\
-		bool __protected = false;				\
-									\
-		if (__kvm) {						\
-			if (is_nvhe_hyp_code() &&			\
-			    !is_protected_kvm_enabled()) 		\
-				__kvm = kern_hyp_va(__kvm); 		\
-									\
-			__protected = kvm_vm_is_protected(__kvm);	\
-		}							\
-		__protected;						\
-	})
-
-#define kvm_vm_is_protected_pkvm(kvm)					\
+#ifdef __KVM_NVHE_HYPERVISOR__
+#define kvm_vm_is_protected(kvm)					\
 	(is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PROTECTED_PKVM))
-
 /*
  * Rely on is_protected_kvm_enabled() check in kvm_vm_is_protected_pkvm() to
  * make sure the vcpu->kvm is always valid VA in the context
  */
-#define vcpu_is_protected_pkvm(vcpu)					\
+#define vcpu_is_protected(vcpu)						\
 	({								\
 		struct kvm *__kvm = READ_ONCE((vcpu)->kvm);		\
-									\
-		(__kvm && kvm_vm_is_protected_pkvm(__kvm));		\
+		(__kvm && kvm_vm_is_protected(__kvm));			\
 	})
-
+#else
+#define kvm_vm_is_protected(kvm)	((kvm)->arch.vm_flavor >= __VM_PROTECTED)
+#define vcpu_is_protected(vcpu)		kvm_vm_is_protected((vcpu)->kvm)
+#endif
 
 #define kvm_vm_is_unprotected_pkvm(kvm)		\
 	(is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PKVM))
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)) {
 		/* Cannot modify memslots once a pVM has run. */
 		if (pkvm_hyp_vm_is_created(kvm) &&
 		    (change == KVM_MR_DELETE || change == KVM_MR_MOVE)) {

-- 
Without deviation from the norm, progress is not possible.