KVM: arm64: Make leaf->leaf PTE changes parallel-aware

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>
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221107215934.1895478-1-oliver.upton@linux.dev

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index b9f0d79..238f293 100644 (file)
--- 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->mmu))
+               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;