linux-kernel - [PATCH v6 5/8] x86/fsgsbase/64: Factor out load FS/GS segments from __switch

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Message-Id: <1537312139-5580-6-git-send-email-chang.seok.bae@intel.com>
Date:   Tue, 18 Sep 2018 16:08:56 -0700
From:   "Chang S. Bae" <chang.seok.bae@...el.com>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Markus T Metzger <markus.t.metzger@...el.com>,
        Ravi Shankar <ravi.v.shankar@...el.com>,
        "Chang S . Bae" <chang.seok.bae@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH v6 5/8] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to()

Instead of open coding the calls to load_seg_legacy(), add
x86_fsgsbase_load() to load FS/GS segments.  When FSGSBASE is
enabled, the new helper will be updated.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Andy Lutomirski <luto@...nel.org>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
---
 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 710f639..31b4755 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -285,6 +285,15 @@ static __always_inline void load_seg_legacy(unsigned short prev_index,
 	}
 }
 
+static __always_inline void x86_fsgsbase_load(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 x86_fsgsbase_read_task(struct task_struct *task,
 					    unsigned short selector)
 {
@@ -595,10 +604,7 @@ __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);
+	x86_fsgsbase_load(prev, next);
 
 	switch_fpu_finish(next_fpu, cpu);
 
-- 
2.7.4