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

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Message-ID: <20200528190718.GA2147934@linux.intel.com>
Date:   Thu, 28 May 2020 22:07:18 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Sean Christopherson <sean.j.christopherson@...el.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 Thu, May 28, 2020 at 07:16:35PM +0200, Borislav Petkov wrote:
> Lemme reply to all mails with one. :-)
> 
> I think Sean almost had it:
> 
> >  sgx_alloc_epc_section -> sgx_map_epc_section
> >  sgx_free_epc_section  -> sgx_unmap_epc_section
> 
> Or even
> 
>   sgx_setup_epc_section()
>   sgx_free_epc_section()

I like these. Lets lock in.

> And except those last two. Those are allocating a page from the EPC
> sections so I'd call them:
> 
> sgx_try_alloc_page    -> sgx_alloc_epc_page_section
> __sgx_try_alloc_page  -> __sgx_alloc_epc_page_section
> 
> former doing the loop, latter doing the per-section list games.

sgx_alloc_epc_page_section() is a bit nasty and long name to use for
grabbing a page. And even the documentation spoke about grabbing before
this naming discussion. I think it is a great description what is going
on.  Everytime I talk about the subject I talk about grabbing.

Lets just say that your suggestion, I could not use in a conference
talk as a verb when I describe what is going on. That function
signature does not fit to my mouth :-) I would talk about
grabbing a page.

This how I refactored yesterday (is in my GIT tree already):

/**
 * sgx_grab_page() - Grab a free EPC page
 * @owner:	the owner of the EPC page
 * @reclaim:	reclaim pages if necessary
 *
 * Iterate through EPC sections and borrow a free EPC page to the caller. When a
 * page is no longer needed it must be released with sgx_free_page(). If
 * @reclaim is set to true, directly reclaim pages when we are out of pages. No
 * mm's can be locked when @reclaim is set to true.
 *
 * Finally, wake up ksgxswapd when the number of pages goes below the watermark
 * before returning back to the caller.
 *
 * Return:
 *   an EPC page,
 *   -errno on error
 */

I also rewrote the kdoc.

I do agree that sgx_try_grab_page() should be renamed as __sgx_grab_page().

/Jarkko