linux-kernel - Re: [PATCH 0/6] Boot-time switching between 4- and 5-level paging for 4.15, Part 1

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Message-ID: <20171023124811.4i73242s5dotnn5k@node.shutemov.name>
Date:   Mon, 23 Oct 2017 15:48:11 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Borislav Petkov <bp@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/6] Boot-time switching between 4- and 5-level paging
 for 4.15, Part 1

On Mon, Oct 23, 2017 at 02:40:14PM +0200, Ingo Molnar wrote:
> 
> * Kirill A. Shutemov <kirill@...temov.name> wrote:
> 
> > > Making a variable that 'looks' like a constant macro dynamic in a rare Kconfig 
> > > scenario is asking for trouble.
> > 
> > We expect boot-time page mode switching to be enabled in kernel of next
> > generation enterprise distros. It shoudn't be that rare.
> 
> My point remains even with not-so-rare Kconfig dependency.

I don't follow how introducing new variable that depends on Kconfig option
would help with the situation.

We would end up with inverse situation: people would use MAX_PHYSMEM_BITS
where the new variable need to be used and we will in the same situation.

-- 
 Kirill A. Shutemov