diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -1691,7 +1691,13 @@
 
 	va = (vm_offset_t)mem;
 	m = PHYS_TO_VM_PAGE(pmap_kextract(va));
-	pmap_remove(kernel_pmap, va, va + bytes);
+
+	/*
+	 * startup_alloc() returns direct-mapped slabs on some platforms.  Avoid
+	 * unmapping ranges of the direct map.
+	 */
+	if (va >= bootstart && va + bytes <= bootmem)
+		pmap_remove(kernel_pmap, va, va + bytes);
 	for (; bytes != 0; bytes -= PAGE_SIZE, m++) {
 #if defined(__aarch64__) || defined(__amd64__) || defined(__mips__) || \
     defined(__riscv) || defined(__powerpc64__)