linux-kernel - Re: [PATCH v30 08/20] x86/sgx: Add functions to allocate and free EPC pages

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Date:   Wed, 27 May 2020 17:52:17 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        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,
        Jethro Beekman <jethro@...tanix.com>
Subject: Re: [PATCH v30 08/20] x86/sgx: Add functions to allocate and free
 EPC pages

On Wed, May 27, 2020 at 10:46:38PM +0200, Borislav Petkov wrote:
> On Tue, May 26, 2020 at 09:21:11PM -0700, Sean Christopherson wrote:
> > In other words, sgx_alloc_epc_section() is poorly named.  It doesn't
> > actually allocate EPC, it allocates kernel structures to map and track EPC.
> > sgx_(un)map_epc_section() would be more accurate and would hopefully
> > alleviate some of the confusion.
> 
> Makes sense.
> 
> > I have no objection to renaming __sgx_alloc_try_alloc_page() to something
> > like sgx_alloc_epc_page_section or whatever, but IMO using get/put will be
> > horrendously confusing.
> 
> Ok. My only issue is that the naming nomenclature sounds strange and
> confusing as it is. "try" in an "alloc" function is kinda tautological -
> of course the function will try to do its best. :)

Heh, so what you're saying is we should add __sgx_really_try_alloc_page()?

> And there are three functions having "alloc" in the name so I can
> imagine someone getting very confused when having to stare at that code.
> 
> So at least naming them in a way so that it is clear what kind of pages
> they "allocate" - i.e., what they actually do - would be a step in the
> right direction...

Ya, and things will only get more confusing when actual NUMA awareness gets
thrown into the mix.

Jarkko, splicing in the NUMA awareness code, what do you think about:

  sgx_alloc_epc_section -> sgx_map_epc_section
  sgx_free_epc_section  -> sgx_unmap_epc_section

  sgx_alloc_page        -> sgx_alloc_epc_page
  sgx_free_page         -> sgx_free_epc_page

  sgx_try_alloc_page    -> sgx_alloc_epc_page_node
  __sgx_try_alloc_page  -> sgx_alloc_epc_page_section