linux-kernel - Re: your "x86: mm: convert dump_pagetables to use walk_page

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Date:   Tue, 12 May 2020 15:18:57 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Price <steven.price@....com>
Cc:     Jan Beulich <jbeulich@...e.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: your "x86: mm: convert dump_pagetables to use walk_page_range"
 change

On Tue, May 12, 2020 at 02:02:51PM +0100, Steven Price wrote:
> > Additionally I'd like to note that note_page()'s "unsigned long val"
> > parameter isn't wide enough for 32-bit PAE PTEs, and hence the NX
> > flag will always be seen as clear in new_prot in such configs.
> 
> Ah, interesting. I'm not sure what type is actually guaranteed to be
> correct. pgprotval_t is x86 specific, but it might be necessary to extend it
> to other architectures. I think I got the "unsigned long" from the generic
> page.h (and because it happens to work on most architectures) - but hadn't
> noticed that that file was specifically only for NOMMU architectures.

unsigned long long should cover the i386-PAE / ARMv7-LPAE cases. I
can't, from teh top of my head, remember if there's anybody else who has
a longer PTE.