Date:   Fri, 7 Jan 2022 14:26:12 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Reinette Chatre <reinette.chatre@intel.com>
Cc:     dave.hansen@linux.intel.com, tglx@linutronix.de, bp@alien8.de,
        luto@kernel.org, mingo@redhat.com, linux-sgx@vger.kernel.org,
        x86@kernel.org, seanjc@google.com, kai.huang@intel.com,
        cathy.zhang@intel.com, cedric.xing@intel.com,
        haitao.huang@intel.com, mark.shanahan@intel.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 07/25] x86/sgx: Move PTE zap code to separate function
Message-ID: <YdgxZFvjrPQN2D8S@iki.fi>
References: <cover.1638381245.git.reinette.chatre@intel.com>
 <bd228c90c139437bb4fcc4b7b99063bfd3eb1439.1638381245.git.reinette.chatre@intel.com>
 <Yavy5JTYAkdZjnK2@iki.fi>
 <66151f3a-0e32-fc57-cb54-5b714588389b@intel.com>
 <917c53ff755d9a20e1f4bcb48c70add8364d1065.camel@kernel.org>
 <192e252a-653f-2221-73dd-99894c134a37@intel.com>
 <YcsleU6ExUbpN51r@iki.fi>
 <cf654da2-00b3-0c3c-57ad-bb669e60de92@intel.com>
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On Thu, Jan 06, 2022 at 09:46:35AM -0800, Reinette Chatre wrote:
> Hi Jarkko,
> 
> On 12/28/2021 6:55 AM, Jarkko Sakkinen wrote:
> > On Mon, Dec 13, 2021 at 02:11:26PM -0800, Reinette Chatre wrote:
> >> 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?
> > 
> > So you have:
> > 
> > "Supporting SGX2 requires this ability to remove page table entries that is
> > available in the SGX reclaimer code"
> > 
> > Just write down where you need this ability (briefly).
> 
> Will do. I will expand the current permission changing text and also add the need
> for this ability when regular pages are changed to TCS pages. TCS pages may not
> be accessed by enclave code so when a regular page becomes a TCS page any page
> table entries pointing to it should be removed.

Thank you, sounds good.

BR,
Jarkko