[PATCH v3 06/15] KVM: arm64: Implement kvm_pgtable_hyp_unmap() at EL2

Quentin Perret
2021-12-01T17:07:36Z

From: Will Deacon <will@kernel.org>

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>
---
arch/arm64/include/asm/kvm_pgtable.h | 21 ++++++++++
arch/arm64/kvm/hyp/pgtable.c | 63 ++++++++++++++++++++++++++++
2 files changed, 84 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 027783829584..9d076f36401d 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -251,6 +251,27 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt);
int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
enum kvm_pgtable_prot prot);

+/**
+ * kvm_pgtable_hyp_unmap() - Remove a mapping from a hypervisor stage-1 page-table.
+ * @pgt: Page-table structure initialised by kvm_pgtable_hyp_init().
+ * @addr: Virtual address from which to remove the mapping.
+ * @size: Size of the mapping.
+ *
+ * The offset of @addr within a page is ignored, @size is rounded-up to
+ * the next page boundary and @phys is rounded-down to the previous page
+ * boundary.
+ *
+ * TLB invalidation is performed for each page-table entry cleared during the
+ * unmapping operation and the reference count for the page-table page
+ * containing the cleared entry is decremented, with unreferenced pages being
+ * freed. The unmapping operation will stop early if it encounters either an
+ * invalid page-table entry or a valid block mapping which maps beyond the range
+ * being unmapped.
+ *
+ * Return: Number of bytes unmapped, which may be 0.
+ */
+u64 kvm_pgtable_hyp_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size);
+
/**
* kvm_get_vtcr() - Helper to construct VTCR_EL2
* @mmfr0: Sanitized value of SYS_ID_AA64MMFR0_EL1 register.
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 768a58835153..6ad4cb2d6947 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -463,6 +463,69 @@ 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)
{
--
2.34.0.rc2.393.gf8c9666880-goog