x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm (7ac7f2c3) · Commits · 戴 / test

arch/x86/include/asm/tlbflush.h

+12 −8

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

		/*

arch/x86/mm/tlb.c

+0 −58

Original line number	Diff line number	Diff line
		@@ -30,7 +30,6 @@

		atomic64_t last_mm_ctx_id = ATOMIC64_INIT(1);

		DEFINE_STATIC_KEY_TRUE(__tlb_defer_switch_to_init_mm);

		static void choose_new_asid(struct mm_struct *next, u64 next_tlb_gen,
		u16 new_asid, bool need_flush)
		@@ -629,60 +628,3 @@ static int __init create_tlb_single_page_flush_ceiling(void)
		return 0;
		}
		late_initcall(create_tlb_single_page_flush_ceiling);

		static ssize_t tlblazy_read_file(struct file file, char __user user_buf,
		size_t count, loff_t *ppos)
		{
		char buf[2];

		buf[0] = static_branch_likely(&__tlb_defer_switch_to_init_mm)
		? '1' : '0';
		buf[1] = '\n';

		return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
		}

		static ssize_t tlblazy_write_file(struct file *file,
		const char __user user_buf, size_t count, loff_t ppos)
		{
		bool val;

		if (kstrtobool_from_user(user_buf, count, &val))
		return -EINVAL;

		if (val)
		static_branch_enable(&__tlb_defer_switch_to_init_mm);
		else
		static_branch_disable(&__tlb_defer_switch_to_init_mm);

		return count;
		}

		static const struct file_operations fops_tlblazy = {
		.read = tlblazy_read_file,
		.write = tlblazy_write_file,
		.llseek = default_llseek,
		};

		static int __init init_tlblazy(void)
		{
		if (boot_cpu_has(X86_FEATURE_PCID)) {
		/*
		* 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 default to trying to defer it in the
		* hopes that we can avoid it entirely. The latter approach
		* runs the risk of receiving otherwise unnecessary IPIs.
		*
		* We can't do this in setup_pcid() because static keys
		* haven't been initialized yet, and it would blow up
		* badly.
		*/
		static_branch_disable(&__tlb_defer_switch_to_init_mm);
		}

		debugfs_create_file("tlb_defer_switch_to_init_mm", S_IRUSR \| S_IWUSR,
		arch_debugfs_dir, NULL, &fops_tlblazy);
		return 0;
		}
		late_initcall(init_tlblazy);

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