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, 1 insertions, 0 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 1a712da1dfa..70d846628bb 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -854,6 +854,7 @@ do_rest:
 #else
         cpu_pda(cpu)->pcurrent = c_idle.idle;
         clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
+        initial_gs = (unsigned long)cpu_pda(cpu);
 #endif
         early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
         initial_code = (unsigned long)start_secondary;