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Subject: Re: [PATCH] x86, powerpc : pkey-mprotect must allow pkey-0
To:     Ram Pai <linuxram@us.ibm.com>, mpe@ellerman.id.au,
        mingo@redhat.com, akpm@linux-foundation.org
References: <1520583161-11741-1-git-send-email-linuxram@us.ibm.com>
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        Ulrich.Weigand@de.ibm.com
From:   Dave Hansen <dave.hansen@intel.com>
Message-ID: <60886e4a-59d4-541a-a6af-d4504e6719ad@intel.com>
Date:   Fri, 9 Mar 2018 14:40:32 -0800
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On 03/09/2018 12:12 AM, Ram Pai wrote:
> Once an address range is associated with an allocated pkey, it cannot be
> reverted back to key-0. There is no valid reason for the above behavior.  On
> the contrary applications need the ability to do so.

Why don't we just set pkey 0 to be allocated in the allocation bitmap by
default?

We *could* also just not let it be special and let it be freed.  An app
could theoretically be careful and make sure nothing is using it.