linux-kernel - Re: linux-next: build warning after merge of the akpm tree

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Message-ID: <20200108145248.GA2584@arm.com>
Date:   Wed, 8 Jan 2020 14:52:49 +0000
From:   Steven Price <steven.price@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: linux-next: build warning after merge of the akpm tree

On Tue, Jan 07, 2020 at 11:11:07PM +0000, Andrew Morton wrote:
> On Mon, 6 Jan 2020 17:07:44 +1100 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> 
> > Hi all,
> > 
> > After merging the akpm tree, today's linux-next build (x86_64
> > allmodconfig) produced this warning:
> > 
> > arch/x86/mm/dump_pagetables.c: In function 'ptdump_walk_pgd_level_core':
> > arch/x86/mm/dump_pagetables.c:403:1: warning: the frame size of 2128 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >   403 | }
> >       | ^
> > 
> > Introduced by commit
> > 
> >   710fae4f03f2 ("x86: mm: convert dump_pagetables to use walk_page_range")
> > 
> 
> (gdb) p sizeof(struct mm_struct)
> $1 = 1664
> 
> yup, that'll do it.

Ok, looks like I'll have to do something a little bit more clever than
the "fake_mm" hack I used before. The trouble is x86 now has two PGDs
due to the PAGE_TABLE_ISOLATION feature. I was trying to isolate this
quirk to the x86 code, but it looks like we need some way of passing an
"override" down for the PGD.

I'll post a possible fix as a reply to this post.

Steve