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Date:   Thu, 17 Jan 2019 10:39:50 +0100
From:   Pavel Machek <pavel@ucw.cz>
To:     Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc:     Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        Nadav Amit <nadav.amit@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>, linux_dti@icloud.com,
        linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org, akpm@linux-foundation.org,
        kernel-hardening@lists.openwall.com, linux-mm@kvack.org,
        will.deacon@arm.com, ard.biesheuvel@linaro.org,
        kristen@linux.intel.com, deneen.t.dock@intel.com,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH 14/17] mm: Make hibernate handle unmapped pages
Message-ID: <20190117093950.GA17930@amd>
References: <20190117003259.23141-1-rick.p.edgecombe@intel.com>
 <20190117003259.23141-15-rick.p.edgecombe@intel.com>
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Hi!

> For architectures with CONFIG_ARCH_HAS_SET_ALIAS, pages can be unmapped
> briefly on the directmap, even when CONFIG_DEBUG_PAGEALLOC is not configu=
red.
> So this changes kernel_map_pages and kernel_page_present to be defined wh=
en
> CONFIG_ARCH_HAS_SET_ALIAS is defined as well. It also changes places
> (page_alloc.c) where those functions are assumed to only be implemented w=
hen
> CONFIG_DEBUG_PAGEALLOC is defined.

Which architectures are that?

Should this be merged to the patch where HAS_SET_ALIAS is introduced? We
don't want broken hibernation in between....


> -#ifdef CONFIG_DEBUG_PAGEALLOC
>  extern bool _debug_pagealloc_enabled;
> -extern void __kernel_map_pages(struct page *page, int numpages, int enab=
le);
> =20
>  static inline bool debug_pagealloc_enabled(void)
>  {
> -	return _debug_pagealloc_enabled;
> +	return IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) && _debug_pagealloc_enabled;
>  }

This will break build AFAICT. _debug_pagealloc_enabled variable does
not exist in !CONFIG_DEBUG_PAGEALLOC case.

									Pavel

--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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