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From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 22 Jun 2016 13:46:18 -0700
Message-ID: <CALCETrULT6Kp_sA4+3=MgFoS0WSzfCmzPvk8dj89raqLC86XKw@mail.gmail.com>
Subject: Re: JITs and 52-bit VA
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Sender: owner-linux-mm@kvack.org
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To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Christopher Covington <cov@codeaurora.org>, Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>, Linaro Dev Mailman List <linaro-dev@lists.linaro.org>, Arnd Bergmann <arnd.bergmann@linaro.org>, Mark Brown <broonie@linaro.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Dmitry Safonov <dsafonov@virtuozzo.com>

On Wed, Jun 22, 2016 at 12:44 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> On Wed, Jun 22, 2016 at 12:20:13PM -0700, Andy Lutomirski wrote:
>> >>
>> >> As an example, a 32-bit x86 program really could have something mapped
>> >> above the 32-bit boundary.  It just wouldn't be useful, but the kernel
>> >> should still understand that it's *user* memory.
>> >>
>> >> So you'd have PR_SET_MMAP_LIMIT and PR_GET_MMAP_LIMIT or similar instead.
>> >
>> > +1. Also it might be (not sure though, just guessing) suitable to do such
>> > thing via memory cgroup controller, instead of carrying this limit per
>> > each process (or task structure/vma or mm).
>>
>> I think we'll want this per mm.  After all, a high-VA-limit-aware bash
>> should be able run high-VA-unaware programs without fiddling with
>> cgroups.
>
> Wait. You mean to have some flag in mm struct and consider
> its value on mmap call?

Exactly.

--Andy

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