linux-kernel - Re: [PATCH 13/25] x86/sgx: Support adding of pages to initialized enclave

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Message-ID: <Ycslvzx4He2Ophqa@iki.fi>
Date:   Tue, 28 Dec 2021 16:57:03 +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 13/25] x86/sgx: Support adding of pages to initialized
 enclave

On Mon, Dec 13, 2021 at 02:12:57PM -0800, Reinette Chatre wrote:
> Hi Jarkko,
> 
> On 12/11/2021 12:00 AM, Jarkko Sakkinen wrote:
> > On Mon, 2021-12-06 at 13:44 -0800, Reinette Chatre wrote:
> > > On 12/4/2021 3:13 PM, Jarkko Sakkinen wrote:
> > > > On Wed, Dec 01, 2021 at 11:23:11AM -0800, Reinette Chatre wrote:
> 
> ...
> 
> > > > > Accessing an uninitialized address from outside the enclave also triggers
> > > > > this flow but the page will remain in PENDING state until accepted from
> > > > > within the enclave.
> > > > 
> > > > What does it mean being in PENDING state, and more imporantly, what is
> > > > PENDING state? What does a memory access within enclave cause when it
> > > > touch a page within this state?
> > > 
> > > The PENDING state is the enclave page state from the SGX hardware's
> > > perspective. The OS uses the ENCLS[EAUG] SGX2 function to add a new page
> > > to the enclave but from the SGX hardware's perspective it would be in a
> > > PENDING state until the enclave accepts the page. An access to the page
> > > in PENDING state would result in a page fault.
> > > 
> > > 
> > > > I see a lot of text in the commit message but zero mentions about EPCM
> > > > expect this one sudden mention about PENDING field without attaching
> > > > it to anything concrete.
> > > 
> > > My apologies - I will add this to this changelog. This matches your
> > > request to describe the __eaug() wrapper introduced in patch 02/25.
> > > Would you like me to duplicate this information here and in that patch
> > > (a new patch dedicated to the __eaug() wrapper) or would you be ok if I
> > > introduce the wrappers all together briefly as in the example you
> > > provide and then detail the flows where the wrappers are used - like
> > > this patch?
> > 
> > I think it would be a good place to describe these details in 02/25,
> > and skip them in rest of the patches.
> > 
> 
> Will do. I do think describing this amount of detail for the new SGX2
> functions would be too much for a single patch so I currently plan to split
> that (02/25) patch into a new patch per SGX2 instruction. Is that ok with
> you or would you like to keep it in a single patch?

It's ok for me.

/Jarkko