On Thursday 15 Jul 2021 at 17:31:47 (+0100), Marc Zyngier wrote:

+struct s2_walk_data {
+	kvm_pte_t	pteval;
+	u32		level;
+};
+
+static int s2_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+		     enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+	struct s2_walk_data *data = arg;
+
+	data->level = level;
+	data->pteval = *ptep;
+	return 0;
+}
+
+/* Assumes mmu_lock taken */
+static bool __check_ioguard_page(struct kvm_vcpu *vcpu, gpa_t ipa)
+{
+	struct s2_walk_data data;
+	struct kvm_pgtable_walker walker = {
+		.cb             = s2_walker,
+		.flags          = KVM_PGTABLE_WALK_LEAF,
+		.arg            = &data,
+	};
+
+	kvm_pgtable_walk(vcpu->arch.hw_mmu->pgt, ALIGN_DOWN(ipa, PAGE_SIZE),
+			 PAGE_SIZE, &walker);
+
+	/* Must be a PAGE_SIZE mapping with our annotation */
+	return (BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(data.level)) == PAGE_SIZE &&
+		data.pteval == MMIO_NOTE);

Nit: you could do this check in the walker directly and check the return
value of kvm_pgtable_walk() instead. That would allow to get rid of
struct s2_walk_data.

Also, though the compiler might be able to optimize, maybe simplify the
level check to level == (KVM_PGTABLE_MAX_LEVELS - 1)?

Thanks,
Quentin

+}

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