Re: [PATCH v5 4/8] x86/mm/tlb: Flush remote and local TLBs concurrently

[Nadav Amit]

> On Feb 16, 2021, at 4:10 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> On Tue, Feb 09, 2021 at 02:16:49PM -0800, Nadav Amit wrote:
>> @@ -816,8 +821,8 @@ STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask,
>> 	 * doing a speculative memory access.
>> 	 */
>> 	if (info->freed_tables) {
>> -		smp_call_function_many(cpumask, flush_tlb_func,
>> -			       (void *)info, 1);
>> +		on_each_cpu_cond_mask(NULL, flush_tlb_func, (void *)info, true,
>> +				      cpumask);
>> 	} else {
>> 		/*
>> 		 * Although we could have used on_each_cpu_cond_mask(),
>> @@ -844,14 +849,15 @@ STATIC_NOPV void native_flush_tlb_others(const struct cpumask *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);
>> +		on_each_cpu_cond_mask(NULL, flush_tlb_func, (void *)info, true,
>> +				      cpumask);
>> 	}
>> }
> 
> Surely on_each_cpu_mask() is more appropriate? There the compiler can do
> the NULL propagation because it's on the same TU.
> 
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -821,8 +821,7 @@ STATIC_NOPV void native_flush_tlb_multi(
> 	 * doing a speculative memory access.
> 	 */
> 	if (info->freed_tables) {
> -		on_each_cpu_cond_mask(NULL, flush_tlb_func, (void *)info, true,
> -				      cpumask);
> +		on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true);
> 	} else {
> 		/*
> 		 * Although we could have used on_each_cpu_cond_mask(),
> @@ -849,8 +848,7 @@ STATIC_NOPV void native_flush_tlb_multi(
> 			if (tlb_is_not_lazy(cpu))
> 				__cpumask_set_cpu(cpu, cond_cpumask);
> 		}
> -		on_each_cpu_cond_mask(NULL, flush_tlb_func, (void *)info, true,
> -				      cpumask);
> +		on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true);
> 	}
> }

Indeed, and there is actually an additional bug - I used cpumask in the
second on_each_cpu_cond_mask() instead of cond_cpumask.