[PATCH v3 03/21] KVM: arm64: Add support for creating kernel-agnostic stage-1 page tables

Will Deacon
2020-08-25T09:42:20Z

The generic page-table walker is pretty useless as it stands, because it
doesn't understand enough to allocate anything. Teach it about stage-1
page-tables, and hook up an API for allocating these for the hypervisor
at EL2.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/kvm_pgtable.h | 34 +++++++
arch/arm64/kvm/hyp/pgtable.c | 131 +++++++++++++++++++++++++++
2 files changed, 165 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 51ccbbb0efae..ec9f98527dcc 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -77,6 +77,40 @@ struct kvm_pgtable_walker {
const enum kvm_pgtable_walk_flags flags;
};

+/**
+ * kvm_pgtable_hyp_init() - Initialise a hypervisor stage-1 page-table.
+ * @pgt: Uninitialised page-table structure to initialise.
+ * @va_bits: Maximum virtual address bits.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits);
+
+/**
+ * kvm_pgtable_hyp_destroy() - Destroy an unused hypervisor stage-1 page-table.
+ * @pgt: Page-table structure initialised by kvm_pgtable_hyp_init().
+ *
+ * The page-table is assumed to be unreachable by any hardware walkers prior
+ * to freeing and therefore no TLB invalidation is performed.
+ */
+void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt);
+
+/**
+ * kvm_pgtable_hyp_map() - Install a mapping in a hypervisor stage-1 page-table.
+ * @pgt: Page-table structure initialised by kvm_pgtable_hyp_init().
+ * @addr: Virtual 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.
+ *
+ * If device attributes are not explicitly requested in @prot, then the
+ * mapping will be normal, cacheable.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
+ enum kvm_pgtable_prot prot);
+
/**
* kvm_pgtable_walk() - Walk a page-table.
* @pgt: Page-table structure initialised by kvm_pgtable_*_init().
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 462001bbe028..d75166823ad9 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -24,8 +24,18 @@

#define KVM_PTE_LEAF_ATTR_LO GENMASK(11, 2)

+#define KVM_PTE_LEAF_ATTR_LO_S1_ATTRIDX GENMASK(4, 2)
+#define KVM_PTE_LEAF_ATTR_LO_S1_AP GENMASK(7, 6)
+#define KVM_PTE_LEAF_ATTR_LO_S1_AP_RO 3
+#define KVM_PTE_LEAF_ATTR_LO_S1_AP_RW 1
+#define KVM_PTE_LEAF_ATTR_LO_S1_SH GENMASK(9, 8)
+#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_HI GENMASK(63, 51)

+#define KVM_PTE_LEAF_ATTR_HI_S1_XN BIT(54)
+
struct kvm_pgtable_walk_data {
struct kvm_pgtable *pgt;
struct kvm_pgtable_walker *walker;
@@ -288,3 +298,124 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,

return _kvm_pgtable_walk(&walk_data);
}
+
+struct hyp_map_data {
+ u64 phys;
+ kvm_pte_t attr;
+};
+
+static int hyp_map_set_prot_attr(enum kvm_pgtable_prot prot,
+ struct hyp_map_data *data)
+{
+ bool device = prot & KVM_PGTABLE_PROT_DEVICE;
+ u32 mtype = device ? MT_DEVICE_nGnRE : MT_NORMAL;
+ kvm_pte_t attr = FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_ATTRIDX, mtype);
+ u32 sh = KVM_PTE_LEAF_ATTR_LO_S1_SH_IS;
+ u32 ap = (prot & KVM_PGTABLE_PROT_W) ? KVM_PTE_LEAF_ATTR_LO_S1_AP_RW :
+ KVM_PTE_LEAF_ATTR_LO_S1_AP_RO;
+
+ if (!(prot & KVM_PGTABLE_PROT_R))
+ return -EINVAL;
+
+ if (prot & KVM_PGTABLE_PROT_X) {
+ if (prot & KVM_PGTABLE_PROT_W)
+ return -EINVAL;
+
+ if (device)
+ return -EINVAL;
+ } else {
+ attr |= KVM_PTE_LEAF_ATTR_HI_S1_XN;
+ }
+
+ attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_AP, ap);
+ attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_SH, sh);
+ attr |= KVM_PTE_LEAF_ATTR_LO_S1_AF;
+ data->attr = attr;
+ return 0;
+}
+
+static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
+ kvm_pte_t *ptep, struct hyp_map_data *data)
+{
+ u64 granule = kvm_granule_size(level), phys = data->phys;
+
+ if (!kvm_block_mapping_supported(addr, end, phys, level))
+ return false;
+
+ WARN_ON(!kvm_set_valid_leaf_pte(ptep, phys, data->attr, level));
+ data->phys += granule;
+ return true;
+}
+
+static int hyp_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+ enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+ kvm_pte_t *childp;
+
+ if (hyp_map_walker_try_leaf(addr, end, level, ptep, arg))
+ return 0;
+
+ if (WARN_ON(level == KVM_PGTABLE_MAX_LEVELS - 1))
+ return -EINVAL;
+
+ childp = (kvm_pte_t *)get_zeroed_page(GFP_KERNEL);
+ if (!childp)
+ return -ENOMEM;
+
+ kvm_set_table_pte(ptep, childp);
+ return 0;
+}
+
+int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
+ enum kvm_pgtable_prot prot)
+{
+ int ret;
+ struct hyp_map_data map_data = {
+ .phys = ALIGN_DOWN(phys, PAGE_SIZE),
+ };
+ struct kvm_pgtable_walker walker = {
+ .cb = hyp_map_walker,
+ .flags = KVM_PGTABLE_WALK_LEAF,
+ .arg = &map_data,
+ };
+
+ ret = hyp_map_set_prot_attr(prot, &map_data);
+ if (ret)
+ return ret;
+
+ ret = kvm_pgtable_walk(pgt, addr, size, &walker);
+ dsb(ishst);
+ isb();
+ return ret;
+}
+
+int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits)
+{
+ pgt->pgd = (kvm_pte_t *)get_zeroed_page(GFP_KERNEL);
+ if (!pgt->pgd)
+ return -ENOMEM;
+
+ pgt->ia_bits = va_bits;
+ pgt->start_level = kvm_start_level(va_bits);
+ pgt->mmu = NULL;
+ return 0;
+}
+
+static int hyp_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+ enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+ free_page((unsigned long)kvm_pte_follow(*ptep));
+ return 0;
+}
+
+void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
+{
+ struct kvm_pgtable_walker walker = {
+ .cb = hyp_free_walker,
+ .flags = KVM_PGTABLE_WALK_TABLE_POST,
+ };
+
+ WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker));
+ free_page((unsigned long)pgt->pgd);
+ pgt->pgd = NULL;
+}
--
2.28.0.297.g1956fa8f8d-goog