[tip:x86/urgent] x86/boot: Defer setup_real_mode() to early_initcall time

[tip-bot for Andy Lutomirski <tipbot@zytor.com>]

Commit-ID:  d0de0f685db7faf2ae4597a39a59996dd84e18c7
Gitweb:     http://git.kernel.org/tip/d0de0f685db7faf2ae4597a39a59996dd84e18c7
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 10 Aug 2016 02:29:15 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 11 Aug 2016 11:15:00 +0200

x86/boot: Defer setup_real_mode() to early_initcall time

There's no need to run setup_real_mode() as early as we run it.
Defer it to the same early_initcall that sets up the page
permissions for the real mode code.

This should be a code size reduction.  More importantly, it give us
a longer window in which we can allocate the real mode trampoline.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: Matt Fleming <mfleming@suse.de>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/fd62f0da4f79357695e9bf3e365623736b05f119.1470821230.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/realmode.h |  1 -
 arch/x86/kernel/setup.c         |  2 --
 arch/x86/realmode/init.c        | 15 ++++++++++++---
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index 9c6b890..8d67777 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -59,6 +59,5 @@ extern unsigned char secondary_startup_64[];
 #endif
 
 void reserve_real_mode(void);
-void setup_real_mode(void);
 
 #endif /* _ARCH_X86_REALMODE_H */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 95c8c9c..0fa60f5 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1141,8 +1141,6 @@ void __init setup_arch(char **cmdline_p)
 		/* A CPU has %cr4 if and only if it has CPUID. */
 		mmu_cr4_features = __read_cr4();
 
-	setup_real_mode();
-
 	memblock_set_current_limit(get_max_mapped());
 
 	/*
diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index c5bdc4e..747b71e 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -30,7 +30,7 @@ void __init reserve_real_mode(void)
 	       base, (unsigned long long)mem, size);
 }
 
-void __init setup_real_mode(void)
+static void __init setup_real_mode(void)
 {
 	u16 real_mode_seg;
 	const u32 *rel;
@@ -101,7 +101,7 @@ void __init setup_real_mode(void)
  * need to mark it executable at do_pre_smp_initcalls() at least,
  * thus run it as a early_initcall().
  */
-static int __init set_real_mode_permissions(void)
+static void __init set_real_mode_permissions(void)
 {
 	unsigned char *base = (unsigned char *) real_mode_header;
 	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
@@ -120,7 +120,16 @@ static int __init set_real_mode_permissions(void)
 	set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
 	set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
 	set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
+}
+
+static int __init init_real_mode(void)
+{
+	if (!real_mode_header)
+		panic("Real mode trampoline was not allocated");
+
+	setup_real_mode();
+	set_real_mode_permissions();
 
 	return 0;
 }
-early_initcall(set_real_mode_permissions);
+early_initcall(init_real_mode);