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Subject[PATCH v2 4/8] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to
Date
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@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
---
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
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