linux-kernel - Re: [RFC][PATCH 4/6] arm, mm: Convert arm to generic tlb

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Message-ID: <1299685150.2308.3097.camel@twins>
Date:	Wed, 09 Mar 2011 16:39:10 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-mm@...ck.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...nel.dk>,
	Russell King <rmk@....linux.org.uk>,
	Chris Metcalf <cmetcalf@...era.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [RFC][PATCH 4/6] arm, mm: Convert arm to generic tlb

On Wed, 2011-03-09 at 15:36 +0000, Catalin Marinas wrote:
> On Wed, 2011-03-09 at 15:19 +0000, Peter Zijlstra wrote:
> > On Wed, 2011-03-09 at 15:16 +0000, Catalin Marinas wrote:
> > > Hi Peter,
> > >
> > > On 2 March 2011 17:59, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> > > > --- linux-2.6.orig/arch/arm/include/asm/tlb.h
> > > > +++ linux-2.6/arch/arm/include/asm/tlb.h
> > > [...]
> > > > +__pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, unsigned long addr)
> > > >  {
> > > >        pgtable_page_dtor(pte);
> > > > -       tlb_add_flush(tlb, addr);
> > > >        tlb_remove_page(tlb, pte);
> > > >  }
> > >
> > > I think we still need a tlb_track_range() call here. On the path to
> > > pte_free_tlb() (for example shift_arg_pages ... free_pte_range) there
> > > doesn't seem to be any code setting the tlb->start/end range. Did I
> > > miss anything?
> > 
> > Patch 3 included:
> > 
> > -#define pte_free_tlb(tlb, ptep, address)                       \
> > -       do {                                                    \
> > -               tlb->need_flush = 1;                            \
> > -               __pte_free_tlb(tlb, ptep, address);             \
> > +#define pte_free_tlb(tlb, ptep, address)                                       \
> > +       do {                                                                    \
> > +               tlb->need_flush = 1;                                            \
> > +               tlb_track_range(tlb, address, pmd_addr_end(address, TASK_SIZE));\
> > +               __pte_free_tlb(tlb, ptep, address);                             \
> >         } while (0)
> 
> OK, so the range is tracked. The only issue is that for platforms with a
> folded pmd the range end would go to TASK_SIZE. In this case
> pgd_addr_end() would make more sense (or something like
> PTRS_PER_PTE*PAGE_SIZE).

Urgh, so when pmds are folded pmd_addr_end() doesn't get to be the next
biggest thing?  PTRS_PER_PTE*PAGE_SIZE like things don't work since
there is no guarantee addr is at the beginning of the pmd.

Ok, will try and sort that out.
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