[PATCH v3 4/7] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to

[Chang S. Bae]

Instead of open code, load_fsgs() will cleanup __switch_to
and symmetric with FS/GS segment save. When FSGSBASE
enabled, X86_FEATURE_FSGSBASE check will be incorporated.

Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 arch/x86/kernel/process_64.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e498671..cebf240 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -279,6 +279,15 @@ static __always_inline void load_seg_legacy(unsigned short prev_index,
 	}
 }
 
+static __always_inline void load_fsgs(struct thread_struct *prev,
+				      struct thread_struct *next)
+{
+	load_seg_legacy(prev->fsindex, prev->fsbase,
+			next->fsindex, next->fsbase, FS);
+	load_seg_legacy(prev->gsindex, prev->gsbase,
+			next->gsindex, next->gsbase, GS);
+}
+
 static unsigned long task_seg_base(struct task_struct *task,
 				   unsigned short selector)
 {
@@ -588,10 +597,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	if (unlikely(next->ds | prev->ds))
 		loadsegment(ds, next->ds);
 
-	load_seg_legacy(prev->fsindex, prev->fsbase,
-			next->fsindex, next->fsbase, FS);
-	load_seg_legacy(prev->gsindex, prev->gsbase,
-			next->gsindex, next->gsbase, GS);
+	load_fsgs(prev, next);
 
 	switch_fpu_finish(next_fpu, cpu);
 
-- 
2.7.4