x86: load pointer to pda into %gs while brining up a CPU

[ Based on original patch from Christoph Lameter and Mike Travis. ]

CPU startup code in head_64.S loaded address of a zero page into %gs
for temporary use till pda is loaded but address to the actual pda is
available at the point.  Load the real address directly instead.

This will help unifying percpu and pda handling later on.

This patch is mostly taken from Mike Travis' "x86_64: Fold pda into
per cpu area" patch.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index bc2900ca82c7..76ffba2aa66d 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -26,8 +26,8 @@
 #include <asm/bios_ebda.h>
 #include <asm/trampoline.h>
 
-/* boot cpu pda */
-static struct x8664_pda _boot_cpu_pda;
+/* boot cpu pda, referenced by head_64.S to initialize %gs for boot CPU */
+struct x8664_pda _boot_cpu_pda;
 
 #ifdef CONFIG_SMP
 /*