powerpc/cacheinfo: Warn if cache object chain becomes unordered

This can catch cases where the device tree has gotten mishandled into an inconsistent state at runtime, e.g. the cache nodes for both the source and the destination are present after a migration. Signed-off-by: Nathan Lynch <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Link: https://lore.kernel.org/r/[email protected]
niw · Jul 30, 2020 · 6ec5436 · 6ec5436
1 parent 1b3da8f
commit 6ec5436
Showing 1 changed file with 9 additions and 0 deletions.
diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c
@@ -420,6 +420,15 @@ static void link_cache_lists(struct cache *smaller, struct cache *bigger)
 	}
 
 	smaller->next_local = bigger;
+
+	/*
+	 * The cache->next_local list sorts by level ascending:
+	 * L1d -> L1i -> L2 -> L3 ...
+	 */
+	WARN_ONCE((smaller->level == 1 && bigger->level > 2) ||
+		  (smaller->level > 1 && bigger->level != smaller->level + 1),
+		  "linking L%i cache %pOFP to L%i cache %pOFP; skipped a level?\n",
+		  smaller->level, smaller->ofnode, bigger->level, bigger->ofnode);
 }
 
 static void do_subsidiary_caches_debugcheck(struct cache *cache)