Add a stage2 helper, kvm_pgtable_stage2_create_unlinked(), for
creating unlinked tables (which is the opposite of
kvm_pgtable_stage2_free_unlinked()). Creating an unlinked table is
useful for splitting PMD and PUD blocks into subtrees of PAGE_SIZE
PTEs. For example, a PUD can be split into PAGE_SIZE PTEs by first
creating a fully populated tree, and then use it to replace the PUD in
a single step. This will be used in a subsequent commit for eager
huge-page splitting (a dirty-logging optimization).
No functional change intended. This new function will be used in a
subsequent commit.
Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_pgtable.h | 28 +++++++++++++++++
arch/arm64/kvm/hyp/pgtable.c | 46 ++++++++++++++++++++++++++++
2 files changed, 74 insertions(+)
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index dcd3aafd3e6c..2b98357a5497 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -460,6 +460,34 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
*/
void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level);
+/**
+ * kvm_pgtable_stage2_create_unlinked() - Create an unlinked stage-2 paging structure.
+ * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
+ * @phys: Physical address of the memory to map.
+ * @level: Starting level of the stage-2 paging structure to be created.
+ * @prot: Permissions and attributes for the mapping.
+ * @mc: Cache of pre-allocated and zeroed memory from which to allocate
+ * page-table pages.
+ * @force_pte: Force mappings to PAGE_SIZE granularity.
+ *
+ * Returns an unlinked page-table tree. If @force_pte is true or
+ * @level is 2 (the PMD level), then the tree is mapped up to the
+ * PAGE_SIZE leaf PTE; the tree is mapped up one level otherwise.
+ * This new page-table tree is not reachable (i.e., it is unlinked)
+ * from the root pgd and it's therefore unreachableby the hardware
+ * page-table walker. No TLB invalidation or CMOs are performed.
+ *
+ * If device attributes are not explicitly requested in @prot, then the
+ * mapping will be normal, cacheable.
+ *
+ * Return: The fully populated (unlinked) stage-2 paging structure, or
+ * an ERR_PTR(error) on failure.
+ */
+kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt,
+ u64 phys, u32 level,
+ enum kvm_pgtable_prot prot,
+ void *mc, bool force_pte);
+
/**
* kvm_pgtable_stage2_map() - Install a mapping in a guest stage-2 page-table.
* @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 0a5ef9288371..3554b74e13c6 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -1181,6 +1181,52 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size)
return kvm_pgtable_walk(pgt, addr, size, &walker);
}
+kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt,
+ u64 phys, u32 level,
+ enum kvm_pgtable_prot prot,
+ void *mc, bool force_pte)
+{
+ struct stage2_map_data map_data = {
+ .phys = phys,
+ .mmu = pgt->mmu,
+ .memcache = mc,
+ .force_pte = force_pte,
+ };
+ struct kvm_pgtable_walker walker = {
+ .cb = stage2_map_walker,
+ .flags = KVM_PGTABLE_WALK_LEAF |
+ KVM_PGTABLE_WALK_SKIP_BBM |
+ KVM_PGTABLE_WALK_SKIP_CMO,
+ .arg = &map_data,
+ };
+ /* .addr (the IPA) is irrelevant for an unlinked table */
+ struct kvm_pgtable_walk_data data = {
+ .walker = &walker,
+ .addr = 0,
+ .end = kvm_granule_size(level),
+ };
+ struct kvm_pgtable_mm_ops *mm_ops = pgt->mm_ops;
+ kvm_pte_t *pgtable;
+ int ret;
+
+ ret = stage2_set_prot_attr(pgt, prot, &map_data.attr);
+ if (ret)
+ return ERR_PTR(ret);
+
+ pgtable = mm_ops->zalloc_page(mc);
+ if (!pgtable)
+ return ERR_PTR(-ENOMEM);
+
+ ret = __kvm_pgtable_walk(&data, mm_ops, (kvm_pteref_t)pgtable,
+ level + 1);
+ if (ret) {
+ kvm_pgtable_stage2_free_unlinked(mm_ops, pgtable, level);
+ mm_ops->put_page(pgtable);
+ return ERR_PTR(ret);
+ }
+
+ return pgtable;
+}
int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
struct kvm_pgtable_mm_ops *mm_ops,
--
2.39.2.722.g9855ee24e9-goog
