[PATCH v3 13/15] KVM: arm64: Make leaf->leaf PTE changes parallel-aware

Oliver Upton
2022-10-27T22:23:27Z

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@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 1df858c21b2e..581ba688c6f7 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -804,18 +804,17 @@ 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))
@@ -825,9 +824,8 @@ 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;
--
2.38.1.273.g43a17bfeac-goog