The patch titled
x86_64-mm-relocatable-kernel-support: build-time checking
has been added to the -mm tree. Its filename is
fix-x86_64-mm-relocatable-kernel-support.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: x86_64-mm-relocatable-kernel-support: build-time checking
From: Vivek Goyal <[EMAIL PROTECTED]>
o X86_64 kernel should run from 2MB aligned address for two reasons.
- Performance.
- For relocatable kernels, page tables are updated based on difference
between compile time address and load time physical address.
This difference should be multiple of 2MB as kernel text and data
is mapped using 2MB pages and PMD should be pointing to a 2MB
aligned address. Life is simpler if both compile time and load time
kernel addresses are 2MB aligned.
o Flag the error at compile time if one is trying to build a kernel which
does not meet alignment restrictions.
Signed-off-by: Vivek Goyal <[EMAIL PROTECTED]>
Cc: "Eric W. Biederman" <[EMAIL PROTECTED]>
Cc: Andi Kleen <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
arch/x86_64/kernel/head64.c | 8 ++++++++
include/asm-x86_64/page.h | 1 +
2 files changed, 9 insertions(+)
diff -puN arch/x86_64/kernel/head64.c~fix-x86_64-mm-relocatable-kernel-support
arch/x86_64/kernel/head64.c
--- a/arch/x86_64/kernel/head64.c~fix-x86_64-mm-relocatable-kernel-support
+++ a/arch/x86_64/kernel/head64.c
@@ -62,6 +62,14 @@ void __init x86_64_start_kernel(char * r
{
int i;
+ /*
+ * Make sure kernel is aligned to 2MB address. Catching it at compile
+ * time is better. Change your config file and compile the kernel
+ * for a 2MB aligned address (CONFIG_PHYSICAL_START)
+ */
+ BUILD_BUG_ON(ALIGN(CONFIG_PHYSICAL_START, __KERNEL_ALIGN)
+ != CONFIG_PHYSICAL_START);
+
/* clear bss before set_intr_gate with early_idt_handler */
clear_bss();
diff -puN include/asm-x86_64/page.h~fix-x86_64-mm-relocatable-kernel-support
include/asm-x86_64/page.h
--- a/include/asm-x86_64/page.h~fix-x86_64-mm-relocatable-kernel-support
+++ a/include/asm-x86_64/page.h
@@ -78,6 +78,7 @@ extern unsigned long phys_base;
#endif /* !__ASSEMBLY__ */
#define __PHYSICAL_START CONFIG_PHYSICAL_START
+#define __KERNEL_ALIGN 0x200000
#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START)
#define __START_KERNEL_map 0xffffffff80000000
#define __PAGE_OFFSET 0xffff810000000000
_
Patches currently in -mm which might be from [EMAIL PROTECTED] are
fix-i-oat-for-kexec.patch
fix-x86_64-mm-relocatable-kernel-support.patch
kdump-kexec-calculate-note-size-at-compile-time.patch
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