* [PATCH 0/3] Fixes on top of the TLB fix in x86/urgent
@ 2017-10-14 16:59 Andy Lutomirski
2017-10-14 16:59 ` [PATCH 1/3] x86/mm/64: Remove the last VM_BUG_ON from the TLB code Andy Lutomirski
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Andy Lutomirski @ 2017-10-14 16:59 UTC (permalink / raw)
To: x86; +Cc: linux-kernel, Borislav Petkov, Andy Lutomirski
I redid the TLB fix to resolve Boris' comments, and then Ingo applied
the old version :-/
Here are my fixes respun on top of the version in -tip. If they pass
muster (they're quite straightforward), can one of you get them to Linus?
(If you disagree with Boris, then skip patch 3.)
Andy Lutomirski (3):
x86/mm/64: Remove the last VM_BUG_ON from the TLB code
x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode"
x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm
arch/x86/include/asm/tlbflush.h | 21 ++++++++++----
arch/x86/mm/tlb.c | 64 ++++-------------------------------------
2 files changed, 21 insertions(+), 64 deletions(-)
--
2.13.6
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH 1/3] x86/mm/64: Remove the last VM_BUG_ON from the TLB code 2017-10-14 16:59 [PATCH 0/3] Fixes on top of the TLB fix in x86/urgent Andy Lutomirski @ 2017-10-14 16:59 ` Andy Lutomirski 2017-10-18 16:23 ` [tip:x86/urgent] x86/mm/64: Remove the last VM_BUG_ON() " tip-bot for Andy Lutomirski 2017-10-14 16:59 ` [PATCH 2/3] x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" Andy Lutomirski 2017-10-14 16:59 ` [PATCH 3/3] x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm Andy Lutomirski 2 siblings, 1 reply; 7+ messages in thread From: Andy Lutomirski @ 2017-10-14 16:59 UTC (permalink / raw) To: x86; +Cc: linux-kernel, Borislav Petkov, Andy Lutomirski Let's avoid hard-to-diagnose crashes in the future. Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/mm/tlb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 658bf0090565..7db23f9f804e 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -147,8 +147,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, this_cpu_write(cpu_tlbstate.is_lazy, false); if (real_prev == next) { - VM_BUG_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) != - next->context.ctx_id); + VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) != + next->context.ctx_id); /* * We don't currently support having a real mm loaded without -- 2.13.6 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [tip:x86/urgent] x86/mm/64: Remove the last VM_BUG_ON() from the TLB code 2017-10-14 16:59 ` [PATCH 1/3] x86/mm/64: Remove the last VM_BUG_ON from the TLB code Andy Lutomirski @ 2017-10-18 16:23 ` tip-bot for Andy Lutomirski 0 siblings, 0 replies; 7+ messages in thread From: tip-bot for Andy Lutomirski @ 2017-10-18 16:23 UTC (permalink / raw) To: linux-tip-commits Cc: mingo, luto, linux-kernel, tglx, hpa, torvalds, peterz, bp Commit-ID: e8b9b0cc8269c85d8167aaee024bfcbb4976c031 Gitweb: https://git.kernel.org/tip/e8b9b0cc8269c85d8167aaee024bfcbb4976c031 Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Sat, 14 Oct 2017 09:59:49 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 18 Oct 2017 15:25:02 +0200 x86/mm/64: Remove the last VM_BUG_ON() from the TLB code Let's avoid hard-to-diagnose crashes in the future. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/f423bbc97864089fbdeb813f1ea126c6eaed844a.1508000261.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/mm/tlb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 658bf00..7db23f9 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -147,8 +147,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, this_cpu_write(cpu_tlbstate.is_lazy, false); if (real_prev == next) { - VM_BUG_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) != - next->context.ctx_id); + VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) != + next->context.ctx_id); /* * We don't currently support having a real mm loaded without ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 2/3] x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" 2017-10-14 16:59 [PATCH 0/3] Fixes on top of the TLB fix in x86/urgent Andy Lutomirski 2017-10-14 16:59 ` [PATCH 1/3] x86/mm/64: Remove the last VM_BUG_ON from the TLB code Andy Lutomirski @ 2017-10-14 16:59 ` Andy Lutomirski 2017-10-18 16:23 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski 2017-10-14 16:59 ` [PATCH 3/3] x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm Andy Lutomirski 2 siblings, 1 reply; 7+ messages in thread From: Andy Lutomirski @ 2017-10-14 16:59 UTC (permalink / raw) To: x86; +Cc: linux-kernel, Borislav Petkov, Andy Lutomirski Due to timezones, commit b956575bed91 ("x86/mm: Flush more aggressively in lazy TLB mode") is an outdated patch that didn't address Borislav's comments. Tidy it up: - The name "tlb_use_lazy_mode" was highly confusing. Change it to "tlb_defer_switch_to_init_mm", which describes what it acutally means. - Move the static_branch crap into a helper. - Improve comments. Actually removing the debugfs option is in the next patch. Fixes: b956575bed91 ("x86/mm: Flush more aggressively in lazy TLB mode") Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/include/asm/tlbflush.h | 7 ++++++- arch/x86/mm/tlb.c | 30 ++++++++++++++++++------------ 2 files changed, 24 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index d362161d3291..0d4a1bb7e303 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -87,7 +87,12 @@ static inline u64 inc_mm_tlb_gen(struct mm_struct *mm) * 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_use_lazy_mode); +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); +} /* * 6 because 6 should be plenty and struct tlb_state will fit in diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 7db23f9f804e..5ee3b59baa85 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -30,7 +30,7 @@ atomic64_t last_mm_ctx_id = ATOMIC64_INIT(1); -DEFINE_STATIC_KEY_TRUE(tlb_use_lazy_mode); +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) @@ -213,6 +213,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, } /* + * Please ignore the name of this function. It should be called + * switch_to_kernel_thread(). + * * enter_lazy_tlb() is a hint from the scheduler that we are entering a * kernel thread or other context without an mm. Acceptable implementations * include doing nothing whatsoever, switching to init_mm, or various clever @@ -227,7 +230,7 @@ void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm) return; - if (static_branch_unlikely(&tlb_use_lazy_mode)) { + if (tlb_defer_switch_to_init_mm()) { /* * There's a significant optimization that may be possible * here. We have accurate enough TLB flush tracking that we @@ -632,7 +635,8 @@ static ssize_t tlblazy_read_file(struct file *file, char __user *user_buf, { char buf[2]; - buf[0] = static_branch_likely(&tlb_use_lazy_mode) ? '1' : '0'; + 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); @@ -647,9 +651,9 @@ static ssize_t tlblazy_write_file(struct file *file, return -EINVAL; if (val) - static_branch_enable(&tlb_use_lazy_mode); + static_branch_enable(&__tlb_defer_switch_to_init_mm); else - static_branch_disable(&tlb_use_lazy_mode); + static_branch_disable(&__tlb_defer_switch_to_init_mm); return count; } @@ -660,23 +664,25 @@ static const struct file_operations fops_tlblazy = { .llseek = default_llseek, }; -static int __init init_tlb_use_lazy_mode(void) +static int __init init_tlblazy(void) { if (boot_cpu_has(X86_FEATURE_PCID)) { /* - * Heuristic: with PCID on, switching to and from - * init_mm is reasonably fast, but remote flush IPIs - * as expensive as ever, so turn off lazy TLB mode. + * 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_use_lazy_mode); + static_branch_disable(&__tlb_defer_switch_to_init_mm); } - debugfs_create_file("tlb_use_lazy_mode", S_IRUSR | S_IWUSR, + debugfs_create_file("tlb_defer_switch_to_init_mm", S_IRUSR | S_IWUSR, arch_debugfs_dir, NULL, &fops_tlblazy); return 0; } -late_initcall(init_tlb_use_lazy_mode); +late_initcall(init_tlblazy); -- 2.13.6 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [tip:x86/urgent] x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" 2017-10-14 16:59 ` [PATCH 2/3] x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" Andy Lutomirski @ 2017-10-18 16:23 ` tip-bot for Andy Lutomirski 0 siblings, 0 replies; 7+ messages in thread From: tip-bot for Andy Lutomirski @ 2017-10-18 16:23 UTC (permalink / raw) To: linux-tip-commits Cc: peterz, tglx, mingo, torvalds, luto, hpa, bp, linux-kernel Commit-ID: 4e57b94664fef55aa71cac33b4632fdfdd52b695 Gitweb: https://git.kernel.org/tip/4e57b94664fef55aa71cac33b4632fdfdd52b695 Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Sat, 14 Oct 2017 09:59:50 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 18 Oct 2017 15:25:02 +0200 x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" Due to timezones, commit: b956575bed91 ("x86/mm: Flush more aggressively in lazy TLB mode") was an outdated patch that well tested and fixed the bug but didn't address Borislav's review comments. Tidy it up: - The name "tlb_use_lazy_mode()" was highly confusing. Change it to "tlb_defer_switch_to_init_mm()", which describes what it actually means. - Move the static_branch crap into a helper. - Improve comments. Actually removing the debugfs option is in the next patch. Reported-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: b956575bed91 ("x86/mm: Flush more aggressively in lazy TLB mode") Link: http://lkml.kernel.org/r/154ef95428d4592596b6e98b0af1d2747d6cfbf8.1508000261.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/include/asm/tlbflush.h | 7 ++++++- arch/x86/mm/tlb.c | 30 ++++++++++++++++++------------ 2 files changed, 24 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index d362161..0d4a1bb 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -87,7 +87,12 @@ static inline u64 inc_mm_tlb_gen(struct mm_struct *mm) * 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_use_lazy_mode); +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); +} /* * 6 because 6 should be plenty and struct tlb_state will fit in diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 7db23f9..5ee3b59 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -30,7 +30,7 @@ atomic64_t last_mm_ctx_id = ATOMIC64_INIT(1); -DEFINE_STATIC_KEY_TRUE(tlb_use_lazy_mode); +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) @@ -213,6 +213,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, } /* + * Please ignore the name of this function. It should be called + * switch_to_kernel_thread(). + * * enter_lazy_tlb() is a hint from the scheduler that we are entering a * kernel thread or other context without an mm. Acceptable implementations * include doing nothing whatsoever, switching to init_mm, or various clever @@ -227,7 +230,7 @@ void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm) return; - if (static_branch_unlikely(&tlb_use_lazy_mode)) { + if (tlb_defer_switch_to_init_mm()) { /* * There's a significant optimization that may be possible * here. We have accurate enough TLB flush tracking that we @@ -632,7 +635,8 @@ static ssize_t tlblazy_read_file(struct file *file, char __user *user_buf, { char buf[2]; - buf[0] = static_branch_likely(&tlb_use_lazy_mode) ? '1' : '0'; + 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); @@ -647,9 +651,9 @@ static ssize_t tlblazy_write_file(struct file *file, return -EINVAL; if (val) - static_branch_enable(&tlb_use_lazy_mode); + static_branch_enable(&__tlb_defer_switch_to_init_mm); else - static_branch_disable(&tlb_use_lazy_mode); + static_branch_disable(&__tlb_defer_switch_to_init_mm); return count; } @@ -660,23 +664,25 @@ static const struct file_operations fops_tlblazy = { .llseek = default_llseek, }; -static int __init init_tlb_use_lazy_mode(void) +static int __init init_tlblazy(void) { if (boot_cpu_has(X86_FEATURE_PCID)) { /* - * Heuristic: with PCID on, switching to and from - * init_mm is reasonably fast, but remote flush IPIs - * as expensive as ever, so turn off lazy TLB mode. + * 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_use_lazy_mode); + static_branch_disable(&__tlb_defer_switch_to_init_mm); } - debugfs_create_file("tlb_use_lazy_mode", S_IRUSR | S_IWUSR, + debugfs_create_file("tlb_defer_switch_to_init_mm", S_IRUSR | S_IWUSR, arch_debugfs_dir, NULL, &fops_tlblazy); return 0; } -late_initcall(init_tlb_use_lazy_mode); +late_initcall(init_tlblazy); ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 3/3] x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm 2017-10-14 16:59 [PATCH 0/3] Fixes on top of the TLB fix in x86/urgent Andy Lutomirski 2017-10-14 16:59 ` [PATCH 1/3] x86/mm/64: Remove the last VM_BUG_ON from the TLB code Andy Lutomirski 2017-10-14 16:59 ` [PATCH 2/3] x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" Andy Lutomirski @ 2017-10-14 16:59 ` Andy Lutomirski 2017-10-18 16:24 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski 2 siblings, 1 reply; 7+ messages in thread From: Andy Lutomirski @ 2017-10-14 16:59 UTC (permalink / raw) To: x86; +Cc: linux-kernel, Borislav Petkov, Andy Lutomirski Borislav thinks that we don't need this knob in a released kernel. Get rid of it. Fixes: b956575bed91 ("x86/mm: Flush more aggressively in lazy TLB mode") Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/include/asm/tlbflush.h | 20 ++++++++------ arch/x86/mm/tlb.c | 58 ----------------------------------------- 2 files changed, 12 insertions(+), 66 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 0d4a1bb7e303..c4aed0de565e 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -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); } /* diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 5ee3b59baa85..0f3d0cea4d00 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -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); -- 2.13.6 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [tip:x86/urgent] x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm 2017-10-14 16:59 ` [PATCH 3/3] x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm Andy Lutomirski @ 2017-10-18 16:24 ` tip-bot for Andy Lutomirski 0 siblings, 0 replies; 7+ messages in thread From: tip-bot for Andy Lutomirski @ 2017-10-18 16:24 UTC (permalink / raw) To: linux-tip-commits Cc: linux-kernel, mingo, hpa, bp, torvalds, luto, tglx, peterz Commit-ID: 7ac7f2c315ef76437f5119df354d334448534fb5 Gitweb: https://git.kernel.org/tip/7ac7f2c315ef76437f5119df354d334448534fb5 Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Sat, 14 Oct 2017 09:59:51 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 18 Oct 2017 15:25:02 +0200 x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm 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: b956575bed91 ("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> --- arch/x86/include/asm/tlbflush.h | 20 ++++++++------ arch/x86/mm/tlb.c | 58 ----------------------------------------- 2 files changed, 12 insertions(+), 66 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 0d4a1bb..c4aed0d 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -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); } /* diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 5ee3b59..0f3d0ce 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -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); ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2017-10-18 16:28 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2017-10-14 16:59 [PATCH 0/3] Fixes on top of the TLB fix in x86/urgent Andy Lutomirski 2017-10-14 16:59 ` [PATCH 1/3] x86/mm/64: Remove the last VM_BUG_ON from the TLB code Andy Lutomirski 2017-10-18 16:23 ` [tip:x86/urgent] x86/mm/64: Remove the last VM_BUG_ON() " tip-bot for Andy Lutomirski 2017-10-14 16:59 ` [PATCH 2/3] x86/mm: Tidy up "x86/mm: Flush more aggressively in lazy TLB mode" Andy Lutomirski 2017-10-18 16:23 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski 2017-10-14 16:59 ` [PATCH 3/3] x86/mm: Remove debug/x86/tlb_defer_switch_to_init_mm Andy Lutomirski 2017-10-18 16:24 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski
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