KVM: arm64: Add support for stage-2 map()/unmap() in generic page-table

Add stage-2 map() and unmap() operations to the generic page-table code.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20200911132529.19844-7-will@kernel.org

arch/arm64/include/asm/kvm_pgtable.h

@@ -140,6 +140,52 @@ int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm *kvm);
  */
 void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
 
+/**
+ * kvm_pgtable_stage2_map() - Install a mapping in a guest stage-2 page-table.
+ * @pgt:	Page-table structure initialised by kvm_pgtable_stage2_init().
+ * @addr:	Intermediate physical address at which to place the mapping.
+ * @size:	Size of the mapping.
+ * @phys:	Physical address of the memory to map.
+ * @prot:	Permissions and attributes for the mapping.
+ * @mc:		Cache of pre-allocated GFP_PGTABLE_USER memory from which to
+ *		allocate page-table pages.
+ *
+ * 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.
+ *
+ * If device attributes are not explicitly requested in @prot, then the
+ * mapping will be normal, cacheable.
+ *
+ * Note that this function will both coalesce existing table entries and split
+ * existing block mappings, relying on page-faults to fault back areas outside
+ * of the new mapping lazily.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
+			   u64 phys, enum kvm_pgtable_prot prot,
+			   struct kvm_mmu_memory_cache *mc);
+
+/**
+ * kvm_pgtable_stage2_unmap() - Remove a mapping from a guest stage-2 page-table.
+ * @pgt:	Page-table structure initialised by kvm_pgtable_stage2_init().
+ * @addr:	Intermediate physical address from which to remove the mapping.
+ * @size:	Size of the mapping.
+ *
+ * The offset of @addr within a page is ignored and @size is rounded-up to
+ * the next 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. Unmapping a cacheable page will ensure that it is clean to the PoC if
+ * FWB is not supported by the CPU.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_stage2_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size);
+
 /**
  * kvm_pgtable_walk() - Walk a page-table.
  * @pgt:	Page-table structure initialised by kvm_pgtable_*_init().

arch/arm64/kvm/hyp/pgtable.c

@@ -32,10 +32,19 @@
 #define KVM_PTE_LEAF_ATTR_LO_S1_SH_IS	3
 #define KVM_PTE_LEAF_ATTR_LO_S1_AF	BIT(10)
 
+#define KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR	GENMASK(5, 2)
+#define KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R	BIT(6)
+#define KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W	BIT(7)
+#define KVM_PTE_LEAF_ATTR_LO_S2_SH	GENMASK(9, 8)
+#define KVM_PTE_LEAF_ATTR_LO_S2_SH_IS	3
+#define KVM_PTE_LEAF_ATTR_LO_S2_AF	BIT(10)
+
 #define KVM_PTE_LEAF_ATTR_HI		GENMASK(63, 51)
 
 #define KVM_PTE_LEAF_ATTR_HI_S1_XN	BIT(54)
 
+#define KVM_PTE_LEAF_ATTR_HI_S2_XN	BIT(54)
+
 struct kvm_pgtable_walk_data {
 	struct kvm_pgtable		*pgt;
 	struct kvm_pgtable_walker	*walker;
@@ -417,6 +426,270 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
 	pgt->pgd = NULL;
 }
 
+struct stage2_map_data {
+	u64				phys;
+	kvm_pte_t			attr;
+
+	kvm_pte_t			*anchor;
+
+	struct kvm_s2_mmu		*mmu;
+	struct kvm_mmu_memory_cache	*memcache;
+};
+
+static int stage2_map_set_prot_attr(enum kvm_pgtable_prot prot,
+				    struct stage2_map_data *data)
+{
+	bool device = prot & KVM_PGTABLE_PROT_DEVICE;
+	kvm_pte_t attr = device ? PAGE_S2_MEMATTR(DEVICE_nGnRE) :
+			    PAGE_S2_MEMATTR(NORMAL);
+	u32 sh = KVM_PTE_LEAF_ATTR_LO_S2_SH_IS;
+
+	if (!(prot & KVM_PGTABLE_PROT_X))
+		attr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
+	else if (device)
+		return -EINVAL;
+
+	if (prot & KVM_PGTABLE_PROT_R)
+		attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;
+
+	if (prot & KVM_PGTABLE_PROT_W)
+		attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;
+
+	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh);
+	attr |= KVM_PTE_LEAF_ATTR_LO_S2_AF;
+	data->attr = attr;
+	return 0;
+}
+
+static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
+				       kvm_pte_t *ptep,
+				       struct stage2_map_data *data)
+{
+	u64 granule = kvm_granule_size(level), phys = data->phys;
+
+	if (!kvm_block_mapping_supported(addr, end, phys, level))
+		return false;
+
+	if (kvm_set_valid_leaf_pte(ptep, phys, data->attr, level))
+		goto out;
+
+	/* There's an existing valid leaf entry, so perform break-before-make */
+	kvm_set_invalid_pte(ptep);
+	kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level);
+	kvm_set_valid_leaf_pte(ptep, phys, data->attr, level);
+out:
+	data->phys += granule;
+	return true;
+}
+
+static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
+				     kvm_pte_t *ptep,
+				     struct stage2_map_data *data)
+{
+	if (data->anchor)
+		return 0;
+
+	if (!kvm_block_mapping_supported(addr, end, data->phys, level))
+		return 0;
+
+	kvm_set_invalid_pte(ptep);
+	kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, 0);
+	data->anchor = ptep;
+	return 0;
+}
+
+static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+				struct stage2_map_data *data)
+{
+	kvm_pte_t *childp, pte = *ptep;
+	struct page *page = virt_to_page(ptep);
+
+	if (data->anchor) {
+		if (kvm_pte_valid(pte))
+			put_page(page);
+
+		return 0;
+	}
+
+	if (stage2_map_walker_try_leaf(addr, end, level, ptep, data))
+		goto out_get_page;
+
+	if (WARN_ON(level == KVM_PGTABLE_MAX_LEVELS - 1))
+		return -EINVAL;
+
+	if (!data->memcache)
+		return -ENOMEM;
+
+	childp = kvm_mmu_memory_cache_alloc(data->memcache);
+	if (!childp)
+		return -ENOMEM;
+
+	/*
+	 * If we've run into an existing block mapping then replace it with
+	 * a table. Accesses beyond 'end' that fall within the new table
+	 * will be mapped lazily.
+	 */
+	if (kvm_pte_valid(pte)) {
+		kvm_set_invalid_pte(ptep);
+		kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level);
+		put_page(page);
+	}
+
+	kvm_set_table_pte(ptep, childp);
+
+out_get_page:
+	get_page(page);
+	return 0;
+}
+
+static int stage2_map_walk_table_post(u64 addr, u64 end, u32 level,
+				      kvm_pte_t *ptep,
+				      struct stage2_map_data *data)
+{
+	int ret = 0;
+
+	if (!data->anchor)
+		return 0;
+
+	free_page((unsigned long)kvm_pte_follow(*ptep));
+	put_page(virt_to_page(ptep));
+
+	if (data->anchor == ptep) {
+		data->anchor = NULL;
+		ret = stage2_map_walk_leaf(addr, end, level, ptep, data);
+	}
+
+	return ret;
+}
+
+/*
+ * This is a little fiddly, as we use all three of the walk flags. The idea
+ * is that the TABLE_PRE callback runs for table entries on the way down,
+ * looking for table entries which we could conceivably replace with a
+ * block entry for this mapping. If it finds one, then it sets the 'anchor'
+ * field in 'struct stage2_map_data' to point at the table entry, before
+ * clearing the entry to zero and descending into the now detached table.
+ *
+ * The behaviour of the LEAF callback then depends on whether or not the
+ * anchor has been set. If not, then we're not using a block mapping higher
+ * up the table and we perform the mapping at the existing leaves instead.
+ * If, on the other hand, the anchor _is_ set, then we drop references to
+ * all valid leaves so that the pages beneath the anchor can be freed.
+ *
+ * Finally, the TABLE_POST callback does nothing if the anchor has not
+ * been set, but otherwise frees the page-table pages while walking back up
+ * the page-table, installing the block entry when it revisits the anchor
+ * pointer and clearing the anchor to NULL.
+ */
+static int stage2_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+			     enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+	struct stage2_map_data *data = arg;
+
+	switch (flag) {
+	case KVM_PGTABLE_WALK_TABLE_PRE:
+		return stage2_map_walk_table_pre(addr, end, level, ptep, data);
+	case KVM_PGTABLE_WALK_LEAF:
+		return stage2_map_walk_leaf(addr, end, level, ptep, data);
+	case KVM_PGTABLE_WALK_TABLE_POST:
+		return stage2_map_walk_table_post(addr, end, level, ptep, data);
+	}
+
+	return -EINVAL;
+}
+
+int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
+			   u64 phys, enum kvm_pgtable_prot prot,
+			   struct kvm_mmu_memory_cache *mc)
+{
+	int ret;
+	struct stage2_map_data map_data = {
+		.phys		= ALIGN_DOWN(phys, PAGE_SIZE),
+		.mmu		= pgt->mmu,
+		.memcache	= mc,
+	};
+	struct kvm_pgtable_walker walker = {
+		.cb		= stage2_map_walker,
+		.flags		= KVM_PGTABLE_WALK_TABLE_PRE |
+				  KVM_PGTABLE_WALK_LEAF |
+				  KVM_PGTABLE_WALK_TABLE_POST,
+		.arg		= &map_data,
+	};
+
+	ret = stage2_map_set_prot_attr(prot, &map_data);
+	if (ret)
+		return ret;
+
+	ret = kvm_pgtable_walk(pgt, addr, size, &walker);
+	dsb(ishst);
+	return ret;
+}
+
+static void stage2_flush_dcache(void *addr, u64 size)
+{
+	if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+		return;
+
+	__flush_dcache_area(addr, size);
+}
+
+static bool stage2_pte_cacheable(kvm_pte_t pte)
+{
+	u64 memattr = FIELD_GET(KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR, pte);
+	return memattr == PAGE_S2_MEMATTR(NORMAL);
+}
+
+static int stage2_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+			       enum kvm_pgtable_walk_flags flag,
+			       void * const arg)
+{
+	struct kvm_s2_mmu *mmu = arg;
+	kvm_pte_t pte = *ptep, *childp = NULL;
+	bool need_flush = false;
+
+	if (!kvm_pte_valid(pte))
+		return 0;
+
+	if (kvm_pte_table(pte, level)) {
+		childp = kvm_pte_follow(pte);
+
+		if (page_count(virt_to_page(childp)) != 1)
+			return 0;
+	} else if (stage2_pte_cacheable(pte)) {
+		need_flush = true;
+	}
+
+	/*
+	 * This is similar to the map() path in that we unmap the entire
+	 * block entry and rely on the remaining portions being faulted
+	 * back lazily.
+	 */
+	kvm_set_invalid_pte(ptep);
+	kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, addr, level);
+	put_page(virt_to_page(ptep));
+
+	if (need_flush) {
+		stage2_flush_dcache(kvm_pte_follow(pte),
+				    kvm_granule_size(level));
+	}
+
+	if (childp)
+		free_page((unsigned long)childp);
+
+	return 0;
+}
+
+int kvm_pgtable_stage2_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size)
+{
+	struct kvm_pgtable_walker walker = {
+		.cb	= stage2_unmap_walker,
+		.arg	= pgt->mmu,
+		.flags	= KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
+	};
+
+	return kvm_pgtable_walk(pgt, addr, size, &walker);
+}
+
 int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm *kvm)
 {
 	size_t pgd_sz;