![Andy Lutomirski](/assets/img/avatar_default.png)
The comment describes the old explicit IPI-based flush logic, which is long gone. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/55e44997e56086528140c5180f8337dc53fb7ffc.1498751203.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
388 lines
10 KiB
C
388 lines
10 KiB
C
#include <linux/init.h>
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#include <linux/mm.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/interrupt.h>
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#include <linux/export.h>
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#include <linux/cpu.h>
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#include <asm/tlbflush.h>
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#include <asm/mmu_context.h>
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#include <asm/cache.h>
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#include <asm/apic.h>
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#include <asm/uv/uv.h>
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#include <linux/debugfs.h>
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/*
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* TLB flushing, formerly SMP-only
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* c/o Linus Torvalds.
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*
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* These mean you can really definitely utterly forget about
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* writing to user space from interrupts. (Its not allowed anyway).
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*
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* Optimizations Manfred Spraul <manfred@colorfullife.com>
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*
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* More scalable flush, from Andi Kleen
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*
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* Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
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*/
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void leave_mm(int cpu)
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{
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struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
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/*
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* It's plausible that we're in lazy TLB mode while our mm is init_mm.
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* If so, our callers still expect us to flush the TLB, but there
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* aren't any user TLB entries in init_mm to worry about.
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*
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* This needs to happen before any other sanity checks due to
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* intel_idle's shenanigans.
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*/
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if (loaded_mm == &init_mm)
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return;
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if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
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BUG();
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switch_mm(NULL, &init_mm, NULL);
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}
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EXPORT_SYMBOL_GPL(leave_mm);
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void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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unsigned long flags;
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local_irq_save(flags);
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switch_mm_irqs_off(prev, next, tsk);
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local_irq_restore(flags);
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}
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void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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unsigned cpu = smp_processor_id();
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struct mm_struct *real_prev = this_cpu_read(cpu_tlbstate.loaded_mm);
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/*
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* NB: The scheduler will call us with prev == next when
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* switching from lazy TLB mode to normal mode if active_mm
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* isn't changing. When this happens, there is no guarantee
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* that CR3 (and hence cpu_tlbstate.loaded_mm) matches next.
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*
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* NB: leave_mm() calls us with prev == NULL and tsk == NULL.
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*/
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this_cpu_write(cpu_tlbstate.state, TLBSTATE_OK);
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if (real_prev == next) {
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/*
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* There's nothing to do: we always keep the per-mm control
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* regs in sync with cpu_tlbstate.loaded_mm. Just
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* sanity-check mm_cpumask.
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*/
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if (WARN_ON_ONCE(!cpumask_test_cpu(cpu, mm_cpumask(next))))
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cpumask_set_cpu(cpu, mm_cpumask(next));
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return;
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}
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if (IS_ENABLED(CONFIG_VMAP_STACK)) {
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/*
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* If our current stack is in vmalloc space and isn't
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* mapped in the new pgd, we'll double-fault. Forcibly
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* map it.
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*/
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unsigned int stack_pgd_index = pgd_index(current_stack_pointer());
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pgd_t *pgd = next->pgd + stack_pgd_index;
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if (unlikely(pgd_none(*pgd)))
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set_pgd(pgd, init_mm.pgd[stack_pgd_index]);
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}
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this_cpu_write(cpu_tlbstate.loaded_mm, next);
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WARN_ON_ONCE(cpumask_test_cpu(cpu, mm_cpumask(next)));
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cpumask_set_cpu(cpu, mm_cpumask(next));
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/*
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* Re-load page tables.
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*
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* This logic has an ordering constraint:
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*
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* CPU 0: Write to a PTE for 'next'
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* CPU 0: load bit 1 in mm_cpumask. if nonzero, send IPI.
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* CPU 1: set bit 1 in next's mm_cpumask
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* CPU 1: load from the PTE that CPU 0 writes (implicit)
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*
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* We need to prevent an outcome in which CPU 1 observes
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* the new PTE value and CPU 0 observes bit 1 clear in
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* mm_cpumask. (If that occurs, then the IPI will never
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* be sent, and CPU 0's TLB will contain a stale entry.)
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*
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* The bad outcome can occur if either CPU's load is
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* reordered before that CPU's store, so both CPUs must
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* execute full barriers to prevent this from happening.
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*
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* Thus, switch_mm needs a full barrier between the
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* store to mm_cpumask and any operation that could load
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* from next->pgd. TLB fills are special and can happen
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* due to instruction fetches or for no reason at all,
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* and neither LOCK nor MFENCE orders them.
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* Fortunately, load_cr3() is serializing and gives the
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* ordering guarantee we need.
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*/
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load_cr3(next->pgd);
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/*
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* This gets called via leave_mm() in the idle path where RCU
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* functions differently. Tracing normally uses RCU, so we have to
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* call the tracepoint specially here.
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*/
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trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
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/* Stop flush ipis for the previous mm */
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WARN_ON_ONCE(!cpumask_test_cpu(cpu, mm_cpumask(real_prev)) &&
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real_prev != &init_mm);
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cpumask_clear_cpu(cpu, mm_cpumask(real_prev));
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/* Load per-mm CR4 and LDTR state */
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load_mm_cr4(next);
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switch_ldt(real_prev, next);
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}
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static void flush_tlb_func_common(const struct flush_tlb_info *f,
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bool local, enum tlb_flush_reason reason)
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{
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/* This code cannot presently handle being reentered. */
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VM_WARN_ON(!irqs_disabled());
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if (this_cpu_read(cpu_tlbstate.state) != TLBSTATE_OK) {
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leave_mm(smp_processor_id());
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return;
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}
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if (f->end == TLB_FLUSH_ALL) {
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local_flush_tlb();
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if (local)
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count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
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trace_tlb_flush(reason, TLB_FLUSH_ALL);
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} else {
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unsigned long addr;
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unsigned long nr_pages = (f->end - f->start) >> PAGE_SHIFT;
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addr = f->start;
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while (addr < f->end) {
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__flush_tlb_single(addr);
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addr += PAGE_SIZE;
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}
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if (local)
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count_vm_tlb_events(NR_TLB_LOCAL_FLUSH_ONE, nr_pages);
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trace_tlb_flush(reason, nr_pages);
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}
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}
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static void flush_tlb_func_local(void *info, enum tlb_flush_reason reason)
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{
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const struct flush_tlb_info *f = info;
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flush_tlb_func_common(f, true, reason);
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}
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static void flush_tlb_func_remote(void *info)
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{
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const struct flush_tlb_info *f = info;
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inc_irq_stat(irq_tlb_count);
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if (f->mm && f->mm != this_cpu_read(cpu_tlbstate.loaded_mm))
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return;
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count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
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flush_tlb_func_common(f, false, TLB_REMOTE_SHOOTDOWN);
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}
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void native_flush_tlb_others(const struct cpumask *cpumask,
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const struct flush_tlb_info *info)
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{
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count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
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if (info->end == TLB_FLUSH_ALL)
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trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
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else
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trace_tlb_flush(TLB_REMOTE_SEND_IPI,
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(info->end - info->start) >> PAGE_SHIFT);
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if (is_uv_system()) {
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unsigned int cpu;
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cpu = smp_processor_id();
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cpumask = uv_flush_tlb_others(cpumask, info);
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if (cpumask)
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smp_call_function_many(cpumask, flush_tlb_func_remote,
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(void *)info, 1);
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return;
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}
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smp_call_function_many(cpumask, flush_tlb_func_remote,
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(void *)info, 1);
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}
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/*
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* See Documentation/x86/tlb.txt for details. We choose 33
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* because it is large enough to cover the vast majority (at
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* least 95%) of allocations, and is small enough that we are
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* confident it will not cause too much overhead. Each single
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* flush is about 100 ns, so this caps the maximum overhead at
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* _about_ 3,000 ns.
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*
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* This is in units of pages.
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*/
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static unsigned long tlb_single_page_flush_ceiling __read_mostly = 33;
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void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
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unsigned long end, unsigned long vmflag)
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{
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int cpu;
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struct flush_tlb_info info = {
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.mm = mm,
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};
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cpu = get_cpu();
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/* Synchronize with switch_mm. */
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smp_mb();
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/* Should we flush just the requested range? */
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if ((end != TLB_FLUSH_ALL) &&
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!(vmflag & VM_HUGETLB) &&
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((end - start) >> PAGE_SHIFT) <= tlb_single_page_flush_ceiling) {
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info.start = start;
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info.end = end;
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} else {
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info.start = 0UL;
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info.end = TLB_FLUSH_ALL;
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}
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if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
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VM_WARN_ON(irqs_disabled());
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local_irq_disable();
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flush_tlb_func_local(&info, TLB_LOCAL_MM_SHOOTDOWN);
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local_irq_enable();
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}
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if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids)
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flush_tlb_others(mm_cpumask(mm), &info);
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put_cpu();
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}
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static void do_flush_tlb_all(void *info)
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{
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count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
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__flush_tlb_all();
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if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
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leave_mm(smp_processor_id());
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}
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void flush_tlb_all(void)
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{
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count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
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on_each_cpu(do_flush_tlb_all, NULL, 1);
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}
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static void do_kernel_range_flush(void *info)
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{
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struct flush_tlb_info *f = info;
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unsigned long addr;
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/* flush range by one by one 'invlpg' */
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for (addr = f->start; addr < f->end; addr += PAGE_SIZE)
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__flush_tlb_single(addr);
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}
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void flush_tlb_kernel_range(unsigned long start, unsigned long end)
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{
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/* Balance as user space task's flush, a bit conservative */
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if (end == TLB_FLUSH_ALL ||
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(end - start) > tlb_single_page_flush_ceiling << PAGE_SHIFT) {
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on_each_cpu(do_flush_tlb_all, NULL, 1);
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} else {
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struct flush_tlb_info info;
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info.start = start;
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info.end = end;
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on_each_cpu(do_kernel_range_flush, &info, 1);
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}
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}
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void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
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{
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struct flush_tlb_info info = {
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.mm = NULL,
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.start = 0UL,
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.end = TLB_FLUSH_ALL,
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};
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int cpu = get_cpu();
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if (cpumask_test_cpu(cpu, &batch->cpumask)) {
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VM_WARN_ON(irqs_disabled());
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local_irq_disable();
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flush_tlb_func_local(&info, TLB_LOCAL_SHOOTDOWN);
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local_irq_enable();
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}
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if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids)
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flush_tlb_others(&batch->cpumask, &info);
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cpumask_clear(&batch->cpumask);
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put_cpu();
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}
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static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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char buf[32];
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unsigned int len;
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len = sprintf(buf, "%ld\n", tlb_single_page_flush_ceiling);
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return simple_read_from_buffer(user_buf, count, ppos, buf, len);
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}
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static ssize_t tlbflush_write_file(struct file *file,
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const char __user *user_buf, size_t count, loff_t *ppos)
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{
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char buf[32];
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ssize_t len;
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int ceiling;
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len = min(count, sizeof(buf) - 1);
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if (copy_from_user(buf, user_buf, len))
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return -EFAULT;
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buf[len] = '\0';
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if (kstrtoint(buf, 0, &ceiling))
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return -EINVAL;
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if (ceiling < 0)
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return -EINVAL;
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tlb_single_page_flush_ceiling = ceiling;
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return count;
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}
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static const struct file_operations fops_tlbflush = {
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.read = tlbflush_read_file,
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.write = tlbflush_write_file,
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.llseek = default_llseek,
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};
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static int __init create_tlb_single_page_flush_ceiling(void)
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{
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debugfs_create_file("tlb_single_page_flush_ceiling", S_IRUSR | S_IWUSR,
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arch_debugfs_dir, NULL, &fops_tlbflush);
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return 0;
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}
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late_initcall(create_tlb_single_page_flush_ceiling);
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