linux-kernel - Re: [PATCH v4 08/13] x86, kasan: clarify kasan's dependency on vmemmap_populate

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Message-ID: <ab8e8aa0-1645-2bc3-52ab-8b071a2a135a@virtuozzo.com>
Date:   Mon, 20 Mar 2017 18:43:03 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        <akpm@...ux-foundation.org>
CC:     <linux-nvdimm@...ts.01.org>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, Nicolai Stange <nicstange@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v4 08/13] x86, kasan: clarify kasan's dependency on
 vmemmap_populate_hugepages()

On 03/16/2017 09:07 AM, Dan Williams wrote:
> Historically kasan has not been careful about whether vmemmap_populate()
> internally allocates a section worth of memmap even if the parameters
> call for less.  For example, a request to shadow map a single page
> results in a full section (128MB) that contains that page being mapped.
> Also, kasan has not been careful to handle cases where this section
> promotion causes overlaps / overrides of previous calls to
> vmemmap_populate().
> 
> Before we teach vmemmap_populate() to support sub-section hotplug,
> arrange for kasan to explicitly avoid vmemmap_populate_basepages().
> This should be functionally equivalent to the current state since
> CONFIG_KASAN requires x86_64 (implies PSE) and it does not collide with
> sub-section hotplug support since CONFIG_KASAN disables
> CONFIG_MEMORY_HOTPLUG.
> 
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Alexander Potapenko <glider@...gle.com>
> Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Reported-by: Nicolai Stange <nicstange@...il.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>