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Date: Wed, 22 Jun 2016 22:44:25 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: JITs and 52-bit VA
Message-ID: <20160622194425.GB2045@uranus.lan>
References: <4A8E6E6D-6CF7-4964-A62E-467AE287D415@linaro.org>
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To: Andy Lutomirski <luto@amacapital.net>
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 12:20:13PM -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?

	Cyrill

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