[PATCH v4 3/3] KVM: arm64: Make stage2_split_walker() skip unnecessary walks

[Leonardo Bras <leo.bras@arm.com>]

Currently, when splitting, all the child nodes will be walked, with the
walker just returning earlier if there is nothing to do. This means all
pagetable entries in the splitting range get a callback from the walker
function, even if it was a level-3 entry.

Optimize splitting by skipping all level-3 entries, as they are already the
smallest block size and can't be split any further.
(i.e. set flag KVM_PGTABLE_WALK_SKIP_LEVEL3)

Signed-off-by: Leonardo Bras <leo.bras@arm.com>
---
 arch/arm64/kvm/hyp/pgtable.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 80744478c810..f75cb666a103 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -1565,21 +1565,22 @@ static int stage2_split_walker(const struct kvm_pgtable_visit_ctx *ctx,
 	new = kvm_init_table_pte(childp, mm_ops);
 	stage2_make_pte(ctx, new);
 	return 0;
 }
 
 int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size,
 			     struct kvm_mmu_memory_cache *mc)
 {
 	struct kvm_pgtable_walker walker = {
 		.cb	= stage2_split_walker,
-		.flags	= KVM_PGTABLE_WALK_LEAF,
+		.flags	= KVM_PGTABLE_WALK_LEAF |
+			  KVM_PGTABLE_WALK_SKIP_LEVEL3,
 		.arg	= mc,
 	};
 	int ret;
 
 	ret = kvm_pgtable_walk(pgt, addr, size, &walker);
 	dsb(ishst);
 	return ret;
 }
 
 int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
-- 
2.55.0