Commit f4550b52 authored Sep 18, 2018 by Chang S. Bae Committed by Ingo Molnar Oct 08, 2018

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@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Markus T Metzger <markus.t.metzger@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Rik van Riel <riel@surriel.com>
Link: http://lkml.kernel.org/r/1537312139-5580-6-git-send-email-chang.seok.bae@intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 824eea38

arch/x86/kernel/process_64.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -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);

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