Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 25 Jul 2018 03:00:52 +0200
From:   Anders Roxell <anders.roxell@linaro.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     tglx@linutronix.de, mingo@kernel.org, songliubraving@fb.com,
        torvalds@linux-foundation.org, riel@surriel.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org, dave.hansen@intel.com,
        linux-tip-commits@vger.kernel.org, rafael.tinoco@linaro.org
Subject: Re: [tip:x86/mm] x86/mm/tlb: Leave lazy TLB mode at page table free
 time
Message-ID: <20180725010052.GA2502@localhost.localdomain>
References: <20180716190337.26133-3-riel@surriel.com>
 <tip-2ff6ddf19c0ec40633bd14d8fe28a289816bd98d@git.kernel.org>
 <20180717114647.GW2476@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20180717114647.GW2476@hirez.programming.kicks-ass.net>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2018-07-17 13:46, Peter Zijlstra wrote:
> 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?

More to that, when building (linux-next tag: next-20180724) on arm 32
there is this build error when CONFIG_MMU is enabled, asm-generic/tlb.h
isn't included, see arch/arm/include/asm/tlb.h.

  CC      mm/memory.o
mm/memory.c: In function ‘tlb_remove_table_smp_sync’:
mm/memory.c:339:2: error: implicit declaration of function ‘tlb_flush_remove_tables_local’; did you mean ‘tlb_remove_table’? [-Werror=implicit-function-declaration]
  tlb_flush_remove_tables_local(mm);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  tlb_remove_table
mm/memory.c: In function ‘tlb_table_flush’:
mm/memory.c:372:2: error: implicit declaration of function ‘tlb_flush_remove_tables’; did you mean ‘tlb_remove_table’? [-Werror=implicit-function-declaration]
  tlb_flush_remove_tables(tlb->mm);
  ^~~~~~~~~~~~~~~~~~~~~~~
  tlb_remove_table


Alternative could be setting in every architecture's asm/tlb.h but that
doesn't make much sense. Other way would be to include prototype in
arch/arm/include/asm/tlb.h, not sure if that would be the best. Is
there any other place this could be defined for fixing issue in arm 32
bit ?


Cheers,
Anders