x86: remove open-coded save/load segment operations

This removes a pile of buggy open-coded implementations of savesegment
and loadsegment.

(They are buggy because they don't have memory barriers to prevent
them from being reordered with respect to memory accesses.)

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index 39eaefbcec06..751850235291 100644
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -480,7 +480,8 @@ void pda_init(int cpu)
         struct x8664_pda *pda = cpu_pda(cpu);
 
         /* Setup up data that may be needed in __get_free_pages early */
-        asm volatile("movl %0,%%fs ; movl %0,%%gs" :: "r" (0));
+        loadsegment(fs, 0);
+        loadsegment(gs, 0);
         /* Memory clobbers used to order PDA accessed */
         mb();
         wrmsrl(MSR_GS_BASE, pda);