[PATCH] x86: Execute WP test after interrupts are enabled

[Pekka Enberg]

Commit 83b519e8b9572c319c8e0c615ee5dd7272856090 ("slab: setup allocators
earlier in the boot sequence") changed the boot sequence to call
mem_init() early. Unfortunately Xen is not prepared to handle the WP test at
that point so we need to make the test run later.

This patch fixes the Xen boot failures reported by Arnd Hannemann.

Reported-by: Arnd Hannemann <hannemann@xxxxxxxxxxxxxxxxxxx>
Tested-by: Arnd Hannemann <hannemann@xxxxxxxxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
---
 arch/x86/Kconfig      |    5 +++++
 arch/x86/mm/init_32.c |   10 +++++++---
 include/linux/mm.h    |    8 ++++++++
 init/main.c           |    1 +
 4 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 13ffa5d..b6ff185 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -50,6 +50,7 @@ config X86
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_LZMA
 	select HAVE_ARCH_KMEMCHECK
+	select HAVE_ARCH_MEM_INIT_LATE if X86_32
 
 config OUTPUT_FORMAT
 	string
@@ -86,6 +87,10 @@ config STACKTRACE_SUPPORT
 config HAVE_LATENCYTOP_SUPPORT
 	def_bool y
 
+config HAVE_ARCH_MEM_INIT_LATE
+	def_bool y
+	depends on X86_32
+
 config FAST_CMPXCHG_LOCAL
 	bool
 	default y
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 3cd7711..488ed4b 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -956,13 +956,17 @@ void __init mem_init(void)
 	BUG_ON(VMALLOC_START				>= VMALLOC_END);
 	BUG_ON((unsigned long)high_memory		> VMALLOC_START);
 
-	if (boot_cpu_data.wp_works_ok < 0)
-		test_wp_bit();
-
 	save_pg_dir();
 	zap_low_mappings(true);
 }
 
+void __init mem_init_late(void)
+{
+	/* Interrupts are enabled at this point. */
+	if (boot_cpu_data.wp_works_ok < 0)
+		test_wp_bit();
+}
+
 #ifdef CONFIG_MEMORY_HOTPLUG
 int arch_add_memory(int nid, u64 start, u64 size)
 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9a72cc7..eefcfbe 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1052,6 +1052,14 @@ extern void si_meminfo(struct sysinfo * val);
 extern void si_meminfo_node(struct sysinfo *val, int nid);
 extern int after_bootmem;
 
+#ifdef CONFIG_HAVE_ARCH_MEM_INIT_LATE
+extern void mem_init_late(void);
+#else
+static inline void mem_init_late(void)
+{
+}
+#endif
+
 #ifdef CONFIG_NUMA
 extern void setup_per_cpu_pageset(void);
 #else
diff --git a/init/main.c b/init/main.c
index 2d9d6bd..45d8dbd 100644
--- a/init/main.c
+++ b/init/main.c
@@ -643,6 +643,7 @@ asmlinkage void __init start_kernel(void)
 	set_gfp_allowed_mask(__GFP_BITS_MASK);
 
 	kmem_cache_init_late();
+	mem_init_late();
 
 	/*
 	 * HACK ALERT! This is early. We're enabling the console before
-- 
1.5.6.3

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