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From: Bhupesh SHARMA <bhupesh.linux@gmail.com>
Date: Mon, 17 Apr 2017 10:18:09 +0530
Message-ID: <CAFTCetT5NcYNop_+X8rnC=pVarBQ=0AGoon7KH-NJq3v3qL8yA@mail.gmail.com>
Subject: Re: [PATCH v3] powerpc: mm: support ARCH_MMAP_RND_BITS
To: Balbir Singh <bsingharora@gmail.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        Bhupesh Sharma <bhsharma@redhat.com>,
        Kees Cook <keescook@chromium.org>, kernel-hardening@lists.openwall.com,
        Alistair Popple <alistair@popple.id.au>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Scott Wood <oss@buserror.net>, Paul Mackerras <paulus@samba.org>,
        Alexander Graf <agraf@suse.com>, Daniel Cashman <dcashman@android.com>,
        Anatolij Gustschin <agust@denx.de>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@lists.ozlabs.org>,
        Daniel Cashman <dcashman@google.com>
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On Thu, Apr 13, 2017 at 12:39 PM, Balbir Singh <bsingharora@gmail.com> wrote:
>>>
>>> Yes. It was derived from TASK_SIZE :
>>>
>>> http://lxr.free-electrons.com/source/arch/powerpc/include/asm/processor.h#L105
>>>
>>
>> That is getting update to 128TB by default and conditionally to 512TB
>>
>
> Since this is compile time, we should probably keep the scope to 128TB
> for now and see if we want to change things at run time later, since
> the expansion is based on a hint. Suggestions?
>

I think this makes sense. If the conditional expansion to 512TB is
protected by a kconfig symbol, we can use the same to have separate
ranges for 128TB and 512TB using the kconfig symbol as the
differentiating factor.

Also please let me know which branch/tree to use where we are done
with the change making the default to 128TB. My v2 was based on
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
(mater branch), where the TASK_SIZE is set to 46-bits inside
'arch/powerpc/include/asm/processor.h'.

So that I can spin the v3 accordingly.

Thanks,
Bhupesh