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

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Date:   Tue, 28 Dec 2021 16:55:53 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Reinette Chatre <reinette.chatre@...el.com>
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

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).

/Jarkko