Subject: Re: linux-next: build failure after merge of the akpm-current tree

From: Andrew Morton <[email-masked]>
Date: Fri, 15 Nov 2019 15:23:52 -0800

On Fri, 15 Nov 2019 18:19:57 +1100 Stephen Rothwell <[email-masked]> wrote:

> Hi all,
> 
> [Also reported by Randy Dunlap]
> 
> After merging the akpm-current tree, today's linux-next build (arm
> multi_v7_defconfig) failed like this:
> 
> mm/vmalloc.c: In function '__purge_vmap_area_lazy':
> mm/vmalloc.c:1286:8: error: 'SHARED_KERNEL_PMD' undeclared (first use in this function)
>  1286 |   if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI))
>       |        ^~~~~~~~~~~~~~~~~
> mm/vmalloc.c:1286:8: note: each undeclared identifier is reported only once for each function it appears in
> mm/vmalloc.c:1286:29: error: implicit declaration of function 'boot_cpu_has' [-Werror=implicit-function-declaration]
>  1286 |   if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI))
>       |                             ^~~~~~~~~~~~
> mm/vmalloc.c:1286:42: error: 'X86_FEATURE_PTI' undeclared (first use in this function)
>  1286 |   if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI))
>       |                                          ^~~~~~~~~~~~~~~
> 
> Caused by commit
> 
>   07ef40e149bf ("mm-vmalloc-fix-regression-caused-by-needless-vmalloc_sync_all-fix")
> 
> SHARED_KERNEL_PMD, boot_cpu_has() and X86_FEATURE_PTI are only defined
> for X86.
> 
> I have reverted that commit for today.

Thanks.  So it has to be an ifdef.

--- a/mm/vmalloc.c~mm-vmalloc-fix-regression-caused-by-needless-vmalloc_sync_all-fix-fix
+++ a/mm/vmalloc.c
@@ -1255,17 +1255,17 @@ static bool __purge_vmap_area_lazy(unsig
 	if (unlikely(valist == NULL))
 		return false;
 
-	if (IS_ENABLED(CONFIG_X86_PAE)) {
-		/*
-		 * First make sure the mappings are removed from all page-tables
-		 * before they are freed.
-		 *
-		 * This is only needed on x86-32 with !SHARED_KERNEL_PMD, which
-		 * is the case on a PAE kernel with PTI enabled.
-		 */
-		if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI))
-			vmalloc_sync_all();
-	}
+#ifdef CONFIG_X86_PAE
+	/*
+	 * First make sure the mappings are removed from all pagetables before
+	 * they are freed.
+	 *
+	 * This is only needed on x86-32 with !SHARED_KERNEL_PMD, which is the
+	 * case on a PAE kernel with PTI enabled.
+	 */
+	if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI))
+		vmalloc_sync_all();
+#endif
 
 	/*
 	 * TODO: to calculate a flush range without looping.
_