KVM: arm64: Implement kvm_pgtable_hyp_unmap() at EL2

Implement kvm_pgtable_hyp_unmap() which can be used to remove hypervisor
stage-1 mappings at EL2.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211215161232.1480836-6-qperret@google.com

1 files changed, 63 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index e50e9158fc56..adc73f8cd24f 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -451,6 +451,69 @@ int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
 	return ret;
 }
 
+struct hyp_unmap_data {
+	u64				unmapped;
+	struct kvm_pgtable_mm_ops	*mm_ops;
+};
+
+static int hyp_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+			    enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+	kvm_pte_t pte = *ptep, *childp = NULL;
+	u64 granule = kvm_granule_size(level);
+	struct hyp_unmap_data *data = arg;
+	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
+
+	if (!kvm_pte_valid(pte))
+		return -EINVAL;
+
+	if (kvm_pte_table(pte, level)) {
+		childp = kvm_pte_follow(pte, mm_ops);
+
+		if (mm_ops->page_count(childp) != 1)
+			return 0;
+
+		kvm_clear_pte(ptep);
+		dsb(ishst);
+		__tlbi_level(vae2is, __TLBI_VADDR(addr, 0), level);
+	} else {
+		if (end - addr < granule)
+			return -EINVAL;
+
+		kvm_clear_pte(ptep);
+		dsb(ishst);
+		__tlbi_level(vale2is, __TLBI_VADDR(addr, 0), level);
+		data->unmapped += granule;
+	}
+
+	dsb(ish);
+	isb();
+	mm_ops->put_page(ptep);
+
+	if (childp)
+		mm_ops->put_page(childp);
+
+	return 0;
+}
+
+u64 kvm_pgtable_hyp_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size)
+{
+	struct hyp_unmap_data unmap_data = {
+		.mm_ops	= pgt->mm_ops,
+	};
+	struct kvm_pgtable_walker walker = {
+		.cb	= hyp_unmap_walker,
+		.arg	= &unmap_data,
+		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
+	};
+
+	if (!pgt->mm_ops->page_count)
+		return 0;
+
+	kvm_pgtable_walk(pgt, addr, size, &walker);
+	return unmap_data.unmapped;
+}
+
 int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits,
 			 struct kvm_pgtable_mm_ops *mm_ops)
 {