linux-kernel - Re: [PATCH v30 07/20] x86/sgx: Enumerate and track EPC sections

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Date:   Thu, 28 May 2020 08:35:15 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-sgx@...r.kernel.org,
        akpm@...ux-foundation.org, dave.hansen@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, josh@...htriplett.org, luto@...nel.org,
        kai.huang@...el.com, rientjes@...gle.com, cedric.xing@...el.com,
        puiterwijk@...hat.com, Serge Ayoun <serge.ayoun@...el.com>,
        Jethro Beekman <jethro@...tanix.com>
Subject: Re: [PATCH v30 07/20] x86/sgx: Enumerate and track EPC sections

On Thu, May 28, 2020 at 08:25:43AM +0300, Jarkko Sakkinen wrote:
> On Tue, May 26, 2020 at 08:56:14PM -0700, Sean Christopherson wrote:
> > On Mon, May 25, 2020 at 11:23:04AM +0200, Borislav Petkov wrote:
> > > On Fri, May 15, 2020 at 03:43:57AM +0300, Jarkko Sakkinen wrote:
> > > > +struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
> > > > +int sgx_nr_epc_sections;
> > > 
> > > We have become very averse against global stuff. What is going to use
> > > those, only sgx code I assume...?
> > 
> > Yes, only SGX code.  The reclaim/swap code needs access to the sections,
> > and that code is in a different file, reclaim.c.  I don't have a super
> > strong objection to sucking reclaim.c into main.c, but I'm somewhat
> > indifferent on code organization as a whole.  Jarkko likely has a stronger
> > opinion.
> 
> I'll change it.
> 
> It's not quite as easy as just "sucking the file in". All the commits
> that touch the file need to be reworked:
> 
> $ git --no-pager log --format="%H %s" arch/x86/kernel/cpu/sgx/reclaim.c
> 5aeca6dabf767e9350ee3188ba25ceb21f3162b4 x86/sgx: Add a page reclaimer
> de9b1088959f36ffdaf43a49bfea1c7f9f81cac7 x86/sgx: Linux Enclave Driver
> 08d8fcb74fe268059ee58fcc2a0833b244e1f22a x86/sgx: Enumerate and track EPC sections

Not that I haven't done this a lot last few years. A proven approach
is to do it in two "git rebase -i mainline/master" sweeps:

1. For each commit, remove reclaim.c entry from the Makefile and import
   reclaim.c contents to main.c.
2. For each commit, delete reclaim.c.

I've tried quite a few different angles and this what I've converged
into. Very hard to hit messy into messy merge conflicts.

/Jarkko