[RESEND PATCH V5 5/8] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to

From: Chang S. Bae
Date: Thu Aug 23 2018 - 12:45:41 EST


Instead of open coding the calls to load_seg_legacy(), add a
load_fsgs() helper to handle fs and gs. When FSGSBASE is enabled,
load_fsgs() will be updated.

Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---
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 bf0bd5c..e014f7d 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