[PATCH v2 13/15] KVM: arm64: Make leaf->leaf PTE changes parallel-aware

[Oliver Upton]

Convert stage2_map_walker_try_leaf() to use the new break-before-make
helpers, thereby making the handler parallel-aware. As before, avoid the
break-before-make if recreating the existing mapping. Additionally,
retry execution if another vCPU thread is modifying the same PTE.

Signed-off-by: Oliver Upton <oliver.upton at linux.dev>
---
 arch/arm64/kvm/hyp/pgtable.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 932134f0d359..adeece227495 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -801,18 +801,17 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
 	else
 		new = kvm_init_invalid_leaf_owner(data->owner_id);
 
-	if (stage2_pte_is_counted(ctx->old)) {
-		/*
-		 * Skip updating the PTE if we are trying to recreate the exact
-		 * same mapping or only change the access permissions. Instead,
-		 * the vCPU will exit one more time from guest if still needed
-		 * and then go through the path of relaxing permissions.
-		 */
-		if (!stage2_pte_needs_update(ctx->old, new))
-			return -EAGAIN;
+	/*
+	 * Skip updating the PTE if we are trying to recreate the exact
+	 * same mapping or only change the access permissions. Instead,
+	 * the vCPU will exit one more time from guest if still needed
+	 * and then go through the path of relaxing permissions.
+	 */
+	if (!stage2_pte_needs_update(ctx->old, new))
+		return -EAGAIN;
 
-		stage2_put_pte(ctx, data->mmu, mm_ops);
-	}
+	if (!stage2_try_break_pte(ctx, data))
+		return -EAGAIN;
 
 	/* Perform CMOs before installation of the guest stage-2 PTE */
 	if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
@@ -822,9 +821,8 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
 	if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
 		mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
 
-	smp_store_release(ctx->ptep, new);
-	if (stage2_pte_is_counted(new))
-		mm_ops->get_page(ctx->ptep);
+	stage2_make_pte(ctx, new);
+
 	if (kvm_phys_is_valid(phys))
 		data->phys += granule;
 	return 0;
-- 
2.38.0.rc1.362.ged0d419d3c-goog