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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/head64.c
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/head64.c')
-rw-r--r--arch/x86/kernel/head64.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 462d0beccb6b..1a311293f733 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -26,12 +26,18 @@
#include <asm/bios_ebda.h>
#include <asm/trampoline.h>
-/* boot cpu pda, referenced by head_64.S to initialize %gs for boot CPU */
+#ifndef CONFIG_SMP
+/* boot cpu pda, referenced by head_64.S to initialize %gs on UP */
struct x8664_pda _boot_cpu_pda;
+#endif
void __init x86_64_init_pda(void)
{
+#ifdef CONFIG_SMP
+ cpu_pda(0) = (void *)__per_cpu_load;
+#else
cpu_pda(0) = &_boot_cpu_pda;
+#endif
cpu_pda(0)->data_offset =
(unsigned long)(__per_cpu_load - __per_cpu_start);
pda_init(0);