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authorTejun Heo <tj@kernel.org>2009-01-13 20:41:35 +0900
committerIngo Molnar <mingo@elte.hu>2009-01-16 14:19:46 +0100
commit1a51e3a0aed18767cf2762e95456ecfeb0bca5e6 (patch)
tree2d930218ef1072a59f7dac0f97bb03aa02796c8c /arch/x86/kernel/vmlinux_64.lds.S
parentc8f3329a0ddd751241e96b4100df7eda14b2cbc6 (diff)
x86: fold pda into percpu area on SMP
[ Based on original patch from Christoph Lameter and Mike Travis. ] Currently pdas and percpu areas are allocated separately. %gs points to local pda and percpu area can be reached using pda->data_offset. This patch folds pda into percpu area. Due to strange gcc requirement, pda needs to be at the beginning of the percpu area so that pda->stack_canary is at %gs:40. To achieve this, a new percpu output section macro - PERCPU_VADDR_PREALLOC() - is added and used to reserve pda sized chunk at the start of the percpu area. After this change, for boot cpu, %gs first points to pda in the data.init area and later during setup_per_cpu_areas() gets updated to point to the actual pda. This means that setup_per_cpu_areas() need to reload %gs for CPU0 while clearing pda area for other cpus as cpu0 already has modified it when control reaches setup_per_cpu_areas(). This patch also removes now unnecessary get_local_pda() and its call sites. A lot of this patch is taken from Mike Travis' "x86_64: Fold pda into per cpu area" patch. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/vmlinux_64.lds.S')
-rw-r--r--arch/x86/kernel/vmlinux_64.lds.S6
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kernel/vmlinux_64.lds.S b/arch/x86/kernel/vmlinux_64.lds.S
index f50280db0df..962f21f1d4d 100644
--- a/arch/x86/kernel/vmlinux_64.lds.S
+++ b/arch/x86/kernel/vmlinux_64.lds.S
@@ -5,6 +5,7 @@
#define LOAD_OFFSET __START_KERNEL_map
#include <asm-generic/vmlinux.lds.h>
+#include <asm/asm-offsets.h>
#include <asm/page.h>
#undef i386 /* in case the preprocessor is a 32bit one */
@@ -215,10 +216,11 @@ SECTIONS
/*
* percpu offsets are zero-based on SMP. PERCPU_VADDR() changes the
* output PHDR, so the next output section - __data_nosave - should
- * switch it back to data.init.
+ * switch it back to data.init. Also, pda should be at the head of
+ * percpu area. Preallocate it.
*/
. = ALIGN(PAGE_SIZE);
- PERCPU_VADDR(0, :percpu)
+ PERCPU_VADDR_PREALLOC(0, :percpu, pda_size)
#else
PERCPU(PAGE_SIZE)
#endif