linux-kernel - Re: [PATCH 5/7] x86,tlb: only send page table free TLB flush to lazy TLB CPUs

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Date:   Sat, 07 Jul 2018 14:26:39 +0200
From:   Mike Galbraith <efault@....de>
To:     Rik van Riel <riel@...riel.com>, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, luto@...nel.org, dave.hansen@...ux.intel.com,
        mingo@...nel.org, kernel-team@...com, tglx@...utronix.de,
        songliubraving@...com, hpa@...or.com
Subject: Re: [PATCH 5/7] x86,tlb: only send page table free TLB flush to
 lazy TLB CPUs

On Fri, 2018-06-29 at 10:29 -0400, Rik van Riel wrote:
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index e59214ec52b1..c4073367219d 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -718,14 +718,47 @@ void tlb_flush_remove_tables_local(void *arg)
>  	}
>  }
>  
> +static void mm_fill_lazy_tlb_cpu_mask(struct mm_struct *mm,
> +				      struct cpumask* lazy_cpus)
> +{
> +	int cpu;
> +
> +	for_each_cpu(cpu, mm_cpumask(mm)) {
> +		if (!per_cpu(cpu_tlbstate.is_lazy, cpu))
> +			cpumask_set_cpu(cpu, lazy_cpus);
> +	}
> +}
> +
>  void tlb_flush_remove_tables(struct mm_struct *mm)
>  {
>  	int cpu = get_cpu();
> +	cpumask_var_t lazy_cpus;
> +
> +	if (cpumask_any_but(mm_cpumask(mm), cpu) >= nr_cpu_ids)
> +		return;

A put_cpu() went missing.

> +
> +	if (!zalloc_cpumask_var(&lazy_cpus, GFP_ATOMIC)) {
> +		/*
> +		 * If the cpumask allocation fails, do a brute force flush
> +		 * on all the CPUs that have this mm loaded.
> +		 */
> +		smp_call_function_many(mm_cpumask(mm),
> +				tlb_flush_remove_tables_local, (void *)mm, 1);
> +		return;
> +	}

Ditto.

	-Mike