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x86/mm/tlb: Restructure switch_mm_irqs_off() 

Move some code that will be needed for the lazy -> !lazy state
transition when a lazy TLB CPU has gotten out of date.

No functional changes, since the if (real_prev == next) branch
always returns.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Rik van Riel <riel@surriel.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: efault@gmx.de
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/r/20180716190337.26133-4-riel@surriel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Rik van Riel 2018-07-16 15:03:33 -04:00 committed by Ingo Molnar
parent 2ff6ddf19c
commit 61d0beb579
1 changed files with 30 additions and 30 deletions
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60
arch/x86/mm/tlb.c
View File

@ -187,6 +187,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
unsigned cpu = smp_processor_id();
u64 next_tlb_gen;
bool need_flush;
u16 new_asid;
/*
* NB: The scheduler will call us with prev == next when switching
@ -252,8 +254,6 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
return;
} else {
u16 new_asid;
bool need_flush;
u64 last_ctx_id = this_cpu_read(cpu_tlbstate.last_ctx_id);
/*
@ -297,41 +297,41 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
next_tlb_gen = atomic64_read(&next->context.tlb_gen);
choose_new_asid(next, next_tlb_gen, &new_asid, &need_flush);
}
if (need_flush) {
this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
load_new_mm_cr3(next->pgd, new_asid, true);
/*
* NB: This gets called via leave_mm() in the idle path
* where RCU functions differently. Tracing normally
* uses RCU, so we need to use the _rcuidle variant.
*
* (There is no good reason for this. The idle code should
* be rearranged to call this before rcu_idle_enter().)
*/
trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
} else {
/* The new ASID is already up to date. */
load_new_mm_cr3(next->pgd, new_asid, false);
/* See above wrt _rcuidle. */
trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, 0);
}
if (need_flush) {
this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
load_new_mm_cr3(next->pgd, new_asid, true);
/*
* Record last user mm's context id, so we can avoid
* flushing branch buffer with IBPB if we switch back
* to the same user.
* NB: This gets called via leave_mm() in the idle path
* where RCU functions differently. Tracing normally
* uses RCU, so we need to use the _rcuidle variant.
*
* (There is no good reason for this. The idle code should
* be rearranged to call this before rcu_idle_enter().)
*/
if (next != &init_mm)
this_cpu_write(cpu_tlbstate.last_ctx_id, next->context.ctx_id);
trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
} else {
/* The new ASID is already up to date. */
load_new_mm_cr3(next->pgd, new_asid, false);
this_cpu_write(cpu_tlbstate.loaded_mm, next);
this_cpu_write(cpu_tlbstate.loaded_mm_asid, new_asid);
/* See above wrt _rcuidle. */
trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, 0);
}
/*
* Record last user mm's context id, so we can avoid
* flushing branch buffer with IBPB if we switch back
* to the same user.
*/
if (next != &init_mm)
this_cpu_write(cpu_tlbstate.last_ctx_id, next->context.ctx_id);
this_cpu_write(cpu_tlbstate.loaded_mm, next);
this_cpu_write(cpu_tlbstate.loaded_mm_asid, new_asid);
load_mm_cr4(next);
switch_ldt(real_prev, next);
}