linux-kernel - [tip:x86/asm] x86/fsgsbase/64: Factor out FS/GS segment loading from __switch

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Date:   Mon, 8 Oct 2018 02:57:08 -0700
From:   "tip-bot for Chang S. Bae" <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     chang.seok.bae@...el.com, riel@...riel.com, bp@...en8.de,
        luto@...capital.net, hpa@...or.com, linux-kernel@...r.kernel.org,
        brgerst@...il.com, tglx@...utronix.de,
        torvalds@...ux-foundation.org, luto@...nel.org,
        dave.hansen@...ux.intel.com, ravi.v.shankar@...el.com,
        ak@...ux.intel.com, mingo@...nel.org, markus.t.metzger@...el.com,
        dvlasenk@...hat.com, peterz@...radead.org
Subject: [tip:x86/asm] x86/fsgsbase/64: Factor out FS/GS segment loading
 from __switch_to()

Commit-ID:  f4550b52e495e1b634d1f2c1004bcea5dc3321ea
Gitweb:     https://git.kernel.org/tip/f4550b52e495e1b634d1f2c1004bcea5dc3321ea
Author:     Chang S. Bae <chang.seok.bae@...el.com>
AuthorDate: Tue, 18 Sep 2018 16:08:56 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 8 Oct 2018 10:41:09 +0200

x86/fsgsbase/64: Factor out FS/GS segment loading from __switch_to()

Instead of open coding the calls to load_seg_legacy(), introduce
x86_fsgsbase_load() to load FS/GS segments.

This makes it more explicit that this is part of FSGSBASE functionality,
and the new helper can be updated when FSGSBASE instructions are enabled.

[ mingo: Wrote new changelog. ]

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: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Markus T Metzger <markus.t.metzger@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>
Cc: Rik van Riel <riel@...riel.com>
Link: http://lkml.kernel.org/r/1537312139-5580-6-git-send-email-chang.seok.bae@intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.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 e5fb0c3dee4d..d6674a425714 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -287,6 +287,15 @@ 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)
 {
@@ -597,10 +606,7 @@ __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);