linux-kernel - Re: [PATCH 07/25] x86/sgx: Move PTE zap code to separate function

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Date:   Mon, 13 Dec 2021 14:11:26 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
CC:     <dave.hansen@...ux.intel.com>, <tglx@...utronix.de>,
        <bp@...en8.de>, <luto@...nel.org>, <mingo@...hat.com>,
        <linux-sgx@...r.kernel.org>, <x86@...nel.org>, <seanjc@...gle.com>,
        <kai.huang@...el.com>, <cathy.zhang@...el.com>,
        <cedric.xing@...el.com>, <haitao.huang@...el.com>,
        <mark.shanahan@...el.com>, <hpa@...or.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/25] x86/sgx: Move PTE zap code to separate function

Hi Jarkko,

On 12/10/2021 11:52 PM, Jarkko Sakkinen wrote:
> On Mon, 2021-12-06 at 13:30 -0800, Reinette Chatre wrote:
>> Hi Jarkko,
>>
>> On 12/4/2021 2:59 PM, Jarkko Sakkinen wrote:
>>> On Wed, Dec 01, 2021 at 11:23:05AM -0800, Reinette Chatre wrote:
>>>> The SGX reclaimer removes page table entries pointing to pages that are
>>>> moved to swap. SGX2 enables changes to pages belonging to an initialized
>>>> enclave, for example changing page permissions. Supporting SGX2 requires
>>>> this ability to remove page table entries that is available in the
>>>> SGX reclaimer code.
>>>
>>> Missing: why SGX2 requirest this?
>>
>> The above paragraph states that SGX2 needs to remove page table entries
>> because it modifies page permissions. Could you please elaborate what is
>> missing?
> 
> It does not say why SGX2 requires an ability to remove page table entries.

Are you saying that modification of EPCM page permissions is not a 
reason to remove page table entries pointing to those pages?

Reinette