x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy()
Open-code on_each_cpu_cond_mask() in native_flush_tlb_others() to optimize the code. Open-coding eliminates the need for the indirect branch that is used to call is_lazy(), and in CPUs that are vulnerable to Spectre v2, it eliminates the retpoline. In addition, it allows to use a preallocated cpumask to compute the CPUs that should be. This would later allow us not to adapt on_each_cpu_cond_mask() to support local and remote functions. Note that calling tlb_is_not_lazy() for every CPU that needs to be flushed, as done in native_flush_tlb_multi() might look ugly, but it is equivalent to what is currently done in on_each_cpu_cond_mask(). Actually, native_flush_tlb_multi() does it more efficiently since it avoids using an indirect branch for the matter. Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://lore.kernel.org/r/20210220231712.2475218-4-namit@vmware.com
This commit is contained in:
Родитель
4c1ba3923e
Коммит
6035152d8e
|
@ -788,11 +788,13 @@ done:
|
|||
nr_invalidate);
|
||||
}
|
||||
|
||||
static bool tlb_is_not_lazy(int cpu, void *data)
|
||||
static bool tlb_is_not_lazy(int cpu)
|
||||
{
|
||||
return !per_cpu(cpu_tlbstate.is_lazy, cpu);
|
||||
}
|
||||
|
||||
static DEFINE_PER_CPU(cpumask_t, flush_tlb_mask);
|
||||
|
||||
STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask,
|
||||
const struct flush_tlb_info *info)
|
||||
{
|
||||
|
@ -813,12 +815,37 @@ STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask,
|
|||
* up on the new contents of what used to be page tables, while
|
||||
* doing a speculative memory access.
|
||||
*/
|
||||
if (info->freed_tables)
|
||||
if (info->freed_tables) {
|
||||
smp_call_function_many(cpumask, flush_tlb_func,
|
||||
(void *)info, 1);
|
||||
else
|
||||
on_each_cpu_cond_mask(tlb_is_not_lazy, flush_tlb_func,
|
||||
(void *)info, 1, cpumask);
|
||||
} else {
|
||||
/*
|
||||
* Although we could have used on_each_cpu_cond_mask(),
|
||||
* open-coding it has performance advantages, as it eliminates
|
||||
* the need for indirect calls or retpolines. In addition, it
|
||||
* allows to use a designated cpumask for evaluating the
|
||||
* condition, instead of allocating one.
|
||||
*
|
||||
* This code works under the assumption that there are no nested
|
||||
* TLB flushes, an assumption that is already made in
|
||||
* flush_tlb_mm_range().
|
||||
*
|
||||
* cond_cpumask is logically a stack-local variable, but it is
|
||||
* more efficient to have it off the stack and not to allocate
|
||||
* it on demand. Preemption is disabled and this code is
|
||||
* non-reentrant.
|
||||
*/
|
||||
struct cpumask *cond_cpumask = this_cpu_ptr(&flush_tlb_mask);
|
||||
int cpu;
|
||||
|
||||
cpumask_clear(cond_cpumask);
|
||||
|
||||
for_each_cpu(cpu, cpumask) {
|
||||
if (tlb_is_not_lazy(cpu))
|
||||
__cpumask_set_cpu(cpu, cond_cpumask);
|
||||
}
|
||||
smp_call_function_many(cond_cpumask, flush_tlb_func, (void *)info, 1);
|
||||
}
|
||||
}
|
||||
|
||||
void flush_tlb_others(const struct cpumask *cpumask,
|
||||
|
|
Загрузка…
Ссылка в новой задаче