linux-kernel - Re: [tip:x86/mm] x86/mm/tlb: Leave lazy TLB mode at page table free time

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Message-ID: <20180717114647.GW2476@hirez.programming.kicks-ass.net>
Date:   Tue, 17 Jul 2018 13:46:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     tglx@...utronix.de, mingo@...nel.org, songliubraving@...com,
        torvalds@...ux-foundation.org, riel@...riel.com, hpa@...or.com,
        linux-kernel@...r.kernel.org, dave.hansen@...el.com
Cc:     linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86/mm/tlb: Leave lazy TLB mode at page table free
 time

On Tue, Jul 17, 2018 at 02:34:07AM -0700, tip-bot for Rik van Riel wrote:
> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> index 3063125197ad..e811ef7b8350 100644
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -303,4 +303,14 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
>  
>  #define tlb_migrate_finish(mm) do {} while (0)
>  
> +/*
> + * Used to flush the TLB when page tables are removed, when lazy
> + * TLB mode may cause a CPU to retain intermediate translations
> + * pointing to about-to-be-freed page table memory.
> + */
> +#ifndef HAVE_TLB_FLUSH_REMOVE_TABLES
> +#define tlb_flush_remove_tables(mm) do {} while (0)
> +#define tlb_flush_remove_tables_local(mm) do {} while (0)
> +#endif

Is there a reason these are not inline functions, which gets us type
checking and the like?