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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sat, 16 May 2020 09:35:57 +0200
Message-ID: <CAK8P3a01FYoWY9sZKU1q=UQ3ut4srwXXUeGRzW6APi+GpoKo1w@mail.gmail.com>
Subject: Re: ARM: static kernel in vmalloc space
To:     afzal mohammed <afzal.mohd.ma@gmail.com>
Cc:     Russell King <linux@armlinux.org.uk>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Sat, May 16, 2020 at 8:06 AM afzal mohammed <afzal.mohd.ma@gmail.com> wrote:
>
> On Thu, May 14, 2020 at 05:32:41PM +0200, Arnd Bergmann wrote:
>
> > Typical distros currently offer two kernels, with and without LPAE,
> > and they probably don't want to add a third one for LPAE with
> > either highmem or vmsplit-4g-4g. Having extra user address
> > space and more lowmem is both going to help users that
> > still have 8GB configurations.
>
> Okay, so the conclusion i take is,
>
> 1. VMSPLIT 4G/4G have to live alongside highmem
> 2. For user space copy, do pinning followed by kmap

Right, though kmap_atomic() should be sufficient here
because it is always a short-lived mapping.

      Arnd