[PATCH v2 3/5] x86/boot: Defer setup_real_mode() to early_initcall time

[Andy Lutomirski]

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 <l...@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 9c6b890d5e7a..8d6777724ba4 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 47006b28cac4..c39a4a28fea1 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1137,8 +1137,6 @@ 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 c5bdc4e473e7..747b71e8f547 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);
-- 
2.7.4