linux-kernel - Re: [PATCH 0/5] Rewrite Motorola MMU page-table layout

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Message-ID: <20200131113139.GC14914@hirez.programming.kicks-ass.net>
Date:   Fri, 31 Jan 2020 12:31:39 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Will Deacon <will@...nel.org>
Cc:     Greg Ungerer <gerg@...ux-m68k.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] Rewrite Motorola MMU page-table layout

On Fri, Jan 31, 2020 at 11:18:24AM +0000, Will Deacon wrote:
> > > > +static inline pgtable_t pte_alloc_one(struct mm_struct *mm)
> > > >  {
> > > >  	struct page *page = alloc_pages(GFP_DMA, 0);
> > > >  	pte_t *pte;

> Does that mean we can drop the GFP_DMA too? If so, this all ends up
> looking very similar to the sun3 code wrt alloc/free and they could
> probably use the same implementation (since the generic code doesn't
> like out pgtable_t definition).

Many software TLB archs have limits on what memory the TLB miss handler
itself can access (chicken-egg issues), it might be this is where the
GFP_DMA comes from.

I can't quickly find this in the CFV4e docs, but I'm not really reading
it carefully either.