KVM: arm64: Add KVM_PGTABLE_S2_AS_S1 flag

Plumb the MT_S2{,_FWB}_AS_S1 memory types into the KVM_S2_MEMATTR()
macro with a new KVM_PGTABLE_S2_AS_S1 flag.

Nobody selects it yet.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260123191637.715429-3-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/include/asm/kvm_pgtable.h

@@ -232,10 +232,12 @@ struct kvm_pgtable_mm_ops {
  * @KVM_PGTABLE_S2_NOFWB:	Don't enforce Normal-WB even if the CPUs have
  *				ARM64_HAS_STAGE2_FWB.
  * @KVM_PGTABLE_S2_IDMAP:	Only use identity mappings.
+ * @KVM_PGTABLE_S2_AS_S1:	Final memory attributes are that of Stage-1.
  */
 enum kvm_pgtable_stage2_flags {
 	KVM_PGTABLE_S2_NOFWB			= BIT(0),
 	KVM_PGTABLE_S2_IDMAP			= BIT(1),
+	KVM_PGTABLE_S2_AS_S1			= BIT(2),
 };
 
 /**

arch/arm64/kvm/hyp/pgtable.c

@@ -659,7 +659,19 @@ void kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu,
 	}
 }
 
-#define KVM_S2_MEMATTR(pgt, attr) PAGE_S2_MEMATTR(attr, stage2_has_fwb(pgt))
+#define KVM_S2_MEMATTR(pgt, attr)					\
+	({								\
+		kvm_pte_t __attr;					\
+									\
+		if ((pgt)->flags & KVM_PGTABLE_S2_AS_S1)		\
+			__attr = PAGE_S2_MEMATTR(AS_S1,			\
+						 stage2_has_fwb(pgt));	\
+		else							\
+			__attr = PAGE_S2_MEMATTR(attr,			\
+						 stage2_has_fwb(pgt));	\
+									\
+		__attr;							\
+	})
 
 static int stage2_set_xn_attr(enum kvm_pgtable_prot prot, kvm_pte_t *attr)
 {