[RFC 08/10] x86/mm: Remove the UP tlbflush code; always use the formerly SMP code

Andy Lutomirski
2017-05-07T22:08:08Z

The UP tlbflush generates somewhat nicer code than the SMP version.
Aside from that, it's fallen quite a bit behind the SMP code:

- flush_tlb_mm_range() didn't flush individual pages if the range
was small.

- The lazy TLB code was much weaker. This usually wouldn't matter,
but, if a kernel thread flushed its lazy "active_mm" more than
once (due to reclaim or similar), it wouldn't be unlazied and
would instead pointlessly flush repeatedly.

- Tracepoints were missing.

Aside from that, simply having the UP code around was a maintanence
burden, since it means that any change to the TLB flush code had to
make sure not to break it.

Simplify everything by deleting the UP code.

Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/Kconfig | 2 +-
arch/x86/include/asm/hardirq.h | 2 +-
arch/x86/include/asm/mmu.h | 6 ---
arch/x86/include/asm/mmu_context.h | 2 -
arch/x86/include/asm/tlbbatch.h | 2 -
arch/x86/include/asm/tlbflush.h | 76 +-------------------------------------
arch/x86/mm/init.c | 2 -
arch/x86/mm/tlb.c | 17 +--------
8 files changed, 5 insertions(+), 104 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2bde14451e54..1b781bcde1a0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -69,7 +69,7 @@ config X86
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
- select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if SMP
+ select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
select ARCH_WANT_FRAME_POINTERS
select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select BUILDTIME_EXTABLE_SORT
diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 59405a248fc2..9b76cd331990 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -22,8 +22,8 @@ typedef struct {
#ifdef CONFIG_SMP
unsigned int irq_resched_count;
unsigned int irq_call_count;
- unsigned int irq_tlb_count;
#endif
+ unsigned int irq_tlb_count;
#ifdef CONFIG_X86_THERMAL_VECTOR
unsigned int irq_thermal_count;
#endif
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index f9813b6d8b80..79b647a7ebd0 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -37,12 +37,6 @@ typedef struct {
#endif
} mm_context_t;

-#ifdef CONFIG_SMP
void leave_mm(int cpu);
-#else
-static inline void leave_mm(int cpu)
-{
-}
-#endif

#endif /* _ASM_X86_MMU_H */
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 68b329d77b3a..187c39470a0b 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -99,10 +99,8 @@ static inline void load_mm_ldt(struct mm_struct *mm)

static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
-#ifdef CONFIG_SMP
if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
this_cpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
-#endif
}

static inline int init_new_context(struct task_struct *tsk,
diff --git a/arch/x86/include/asm/tlbbatch.h b/arch/x86/include/asm/tlbbatch.h
index 01a6de16fb96..f4a6ff352a0e 100644
--- a/arch/x86/include/asm/tlbbatch.h
+++ b/arch/x86/include/asm/tlbbatch.h
@@ -3,7 +3,6 @@

#include <linux/cpumask.h>

-#ifdef CONFIG_SMP
struct arch_tlbflush_unmap_batch {
/*
* Each bit set is a CPU that potentially has a TLB entry for one of
@@ -11,6 +10,5 @@ struct arch_tlbflush_unmap_batch {
*/
struct cpumask cpumask;
};
-#endif

#endif /* _ARCH_X86_TLBBATCH_H */
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index c600d2d4a501..3c9289637669 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -7,6 +7,7 @@
#include <asm/processor.h>
#include <asm/cpufeature.h>
#include <asm/special_insns.h>
+#include <asm/smp.h>

static inline void __invpcid(unsigned long pcid, unsigned long addr,
unsigned long type)
@@ -65,10 +66,8 @@ static inline void invpcid_flush_all_nonglobals(void)
#endif

struct tlb_state {
-#ifdef CONFIG_SMP
struct mm_struct *active_mm;
int state;
-#endif

/*
* Access to this CR4 shadow and to H/W CR4 is protected by
@@ -231,77 +230,6 @@ struct flush_tlb_info {
unsigned long end;
};

-#ifndef CONFIG_SMP
-
-/* "_up" is for UniProcessor.
- *
- * This is a helper for other header functions. *Not* intended to be called
- * directly. All global TLB flushes need to either call this, or to bump the
- * vm statistics themselves.
- */
-static inline void __flush_tlb_up(void)
-{
- count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
- __flush_tlb();
-}
-
-static inline void flush_tlb_all(void)
-{
- count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
- __flush_tlb_all();
-}
-
-static inline void local_flush_tlb(void)
-{
- __flush_tlb_up();
-}
-
-static inline void flush_tlb_mm(struct mm_struct *mm)
-{
- if (mm == current->active_mm)
- __flush_tlb_up();
-}
-
-static inline void flush_tlb_page(struct vm_area_struct *vma,
- unsigned long addr)
-{
- if (vma->vm_mm == current->active_mm)
- __flush_tlb_one(addr);
-}
-
-static inline void flush_tlb_range(struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
-{
- if (vma->vm_mm == current->active_mm)
- __flush_tlb_up();
-}
-
-static inline void flush_tlb_mm_range(struct mm_struct *mm,
- unsigned long start, unsigned long end, unsigned long vmflag)
-{
- if (mm == current->active_mm)
- __flush_tlb_up();
-}
-
-static inline void native_flush_tlb_others(const struct cpumask *cpumask,
- const struct flush_tlb_info *info)
-{
-}
-
-static inline void reset_lazy_tlbstate(void)
-{
-}
-
-static inline void flush_tlb_kernel_range(unsigned long start,
- unsigned long end)
-{
- flush_tlb_all();
-}
-
-#else /* SMP */
-
-#include <asm/smp.h>
-
#define local_flush_tlb() __flush_tlb()

#define flush_tlb_mm(mm) flush_tlb_mm_range(mm, 0UL, TLB_FLUSH_ALL, 0UL)
@@ -339,8 +267,6 @@ static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,

extern void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);

-#endif /* SMP */
-
#ifndef CONFIG_PARAVIRT
#define flush_tlb_others(mask, info) \
native_flush_tlb_others(mask, info)
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 2193799ca800..078972129885 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -792,10 +792,8 @@ void __init zone_sizes_init(void)
}

DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate) = {
-#ifdef CONFIG_SMP
.active_mm = &init_mm,
.state = 0,
-#endif
.cr4 = ~0UL, /* fail hard if we screw up cr4 shadow initialization */
};
EXPORT_SYMBOL_GPL(cpu_tlbstate);
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index c03b4a0ce58c..da1416c77bfb 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -15,7 +15,7 @@
#include <linux/debugfs.h>

/*
- * Smarter SMP flushing macros.
+ * TLB flushing, formerly SMP-only
* c/o Linus Torvalds.
*
* These mean you can really definitely utterly forget about
@@ -28,8 +28,6 @@
* Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
*/

-#ifdef CONFIG_SMP
-
/*
* We cannot call mmdrop() because we are in interrupt context,
* instead update mm->cpu_vm_mask.
@@ -53,8 +51,6 @@ void leave_mm(int cpu)
}
EXPORT_SYMBOL_GPL(leave_mm);

-#endif /* CONFIG_SMP */
-
void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
@@ -85,10 +81,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
set_pgd(pgd, init_mm.pgd[stack_pgd_index]);
}

-#ifdef CONFIG_SMP
this_cpu_write(cpu_tlbstate.state, TLBSTATE_OK);
this_cpu_write(cpu_tlbstate.active_mm, next);
-#endif

cpumask_set_cpu(cpu, mm_cpumask(next));

@@ -146,9 +140,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
if (unlikely(prev->context.ldt != next->context.ldt))
load_mm_ldt(next);
#endif
- }
-#ifdef CONFIG_SMP
- else {
+ } else {
this_cpu_write(cpu_tlbstate.state, TLBSTATE_OK);
BUG_ON(this_cpu_read(cpu_tlbstate.active_mm) != next);

@@ -175,11 +167,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
load_mm_ldt(next);
}
}
-#endif
}

-#ifdef CONFIG_SMP
-
/*
* The flush IPI assumes that a thread switch happens in this order:
* [cpu0: the cpu that switches]
@@ -436,5 +425,3 @@ static int __init create_tlb_single_page_flush_ceiling(void)
return 0;
}
late_initcall(create_tlb_single_page_flush_ceiling);
-
-#endif /* CONFIG_SMP */
--
2.9.3