arm64: mm: Tidy up force_pte_mapping()

Tidy up the implementation of force_pte_mapping() to make it easier to
read and introduce the split_leaf_mapping_possible() helper to reduce
code duplication in split_kernel_leaf_mapping() and
arch_kfence_init_pool().

Suggested-by: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Yang Shi <yang@os.amperecomputing.com>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 652bb8c14035e9ce70bcf10a51d73bed83552a2c..2ba01dc8ef822aa01b8c3161064068e0339ea94e 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -710,12 +710,26 @@ out:
 
 static inline bool force_pte_mapping(void)
 {
-       bool bbml2 = system_capabilities_finalized() ?
+       const bool bbml2 = system_capabilities_finalized() ?
                system_supports_bbml2_noabort() : cpu_supports_bbml2_noabort();
 
-       return (!bbml2 && (rodata_full || arm64_kfence_can_set_direct_map() ||
-                          is_realm_world())) ||
-               debug_pagealloc_enabled();
+       if (debug_pagealloc_enabled())
+               return true;
+       if (bbml2)
+               return false;
+       return rodata_full || arm64_kfence_can_set_direct_map() || is_realm_world();
+}
+
+static inline bool split_leaf_mapping_possible(void)
+{
+       /*
+        * !BBML2_NOABORT systems should never run into scenarios where we would
+        * have to split. So exit early and let calling code detect it and raise
+        * a warning.
+        */
+       if (!system_supports_bbml2_noabort())
+               return false;
+       return !force_pte_mapping();
 }
 
 static DEFINE_MUTEX(pgtable_split_lock);
@@ -725,22 +739,11 @@ int split_kernel_leaf_mapping(unsigned long start, unsigned long end)
        int ret;
 
        /*
-        * !BBML2_NOABORT systems should not be trying to change permissions on
-        * anything that is not pte-mapped in the first place. Just return early
-        * and let the permission change code raise a warning if not already
-        * pte-mapped.
-        */
-       if (!system_supports_bbml2_noabort())
-               return 0;
-
-       /*
-        * If the region is within a pte-mapped area, there is no need to try to
-        * split. Additionally, CONFIG_DEBUG_PAGEALLOC and CONFIG_KFENCE may
-        * change permissions from atomic context so for those cases (which are
-        * always pte-mapped), we must not go any further because taking the
-        * mutex below may sleep.
+        * Exit early if the region is within a pte-mapped area or if we can't
+        * split. For the latter case, the permission change code will raise a
+        * warning if not already pte-mapped.
         */
-       if (force_pte_mapping() || is_kfence_address((void *)start))
+       if (!split_leaf_mapping_possible() || is_kfence_address((void *)start))
                return 0;
 
        /*
@@ -1039,7 +1042,7 @@ bool arch_kfence_init_pool(void)
        int ret;
 
        /* Exit early if we know the linear map is already pte-mapped. */
-       if (!system_supports_bbml2_noabort() || force_pte_mapping())
+       if (!split_leaf_mapping_possible())
                return true;
 
        /* Kfence pool is already pte-mapped for the early init case. */