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Message-ID: <97fc1205-4270-1924-d3b3-19708ada648c@intel.com>
Date:   Fri, 28 Jan 2022 15:53:22 -0800
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Subject: Re: [PATCH V8 09/44] x86/pkeys: Enable PKS on cpus which support it
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To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        linux-kernel@vger.kernel.org
References: <20220127175505.851391-1-ira.weiny@intel.com>
 <20220127175505.851391-10-ira.weiny@intel.com>
 <f9db9626-de92-65a4-57f1-cf94511dd137@intel.com>
 <20220128234103.GL785175@iweiny-DESK2.sc.intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20220128234103.GL785175@iweiny-DESK2.sc.intel.com>
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On 1/28/22 15:41, Ira Weiny wrote:
> On Fri, Jan 28, 2022 at 03:18:29PM -0800, Dave Hansen wrote:
>> On 1/27/22 09:54, ira.weiny@intel.com wrote:
>>> Initially, pks_setup() initializes the per-cpu MSR with 0 to enable all
>>> access on all pkeys.
>>
>> Why not just make it restrictive to start out?  That's what we do for PKU.
> 
> This maintains compatibility with the code prior to this patch.  Ie no
> restrictions on kernel mappings.

But, compatibility with what?  At this point, there are no non-pkey-0
kernel mappings.  So, PKRS can be set to anything as long as the two low
bits are clear.