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x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm

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Borislav thinks that we don't need this knob in a released kernel.
Get rid of it.

Requested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: b956575bed ("x86/mm: Flush more aggressively in lazy TLB mode")
Link: http://lkml.kernel.org/r/1fa72431924e81e86c164ff7881bf9240d1f1a6c.1508000261.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski
2017-10-14 09:59:51 -07:00
committed by Ingo Molnar
parent 4e57b94664
commit 7ac7f2c315
2 changed files with 12 additions and 66 deletions
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20
arch/x86/include/asm/tlbflush.h
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@@ -82,16 +82,20 @@ static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
#define __flush_tlb_single(addr) __native_flush_tlb_single(addr)
#endif
/*
* If tlb_use_lazy_mode is true, then we try to avoid switching CR3 to point
* to init_mm when we switch to a kernel thread (e.g. the idle thread). If
* it's false, then we immediately switch CR3 when entering a kernel thread.
*/
DECLARE_STATIC_KEY_TRUE(__tlb_defer_switch_to_init_mm);
static inline bool tlb_defer_switch_to_init_mm(void)
{
return static_branch_unlikely(&__tlb_defer_switch_to_init_mm);
/*
* If we have PCID, then switching to init_mm is reasonably
* fast. If we don't have PCID, then switching to init_mm is
* quite slow, so we try to defer it in the hopes that we can
* avoid it entirely. The latter approach runs the risk of
* receiving otherwise unnecessary IPIs.
*
* This choice is just a heuristic. The tlb code can handle this
* function returning true or false regardless of whether we have
* PCID.
*/
return !static_cpu_has(X86_FEATURE_PCID);
}
/*