linux-kernel - Re: [RFC PATCH 00/12] Ion cleanup in preparation for moving out of staging

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Message-ID: <CA+M3ks6R=n4n54wofK7pYcWoQKUhzyWQytBO90+pRDRrAhi3ww@mail.gmail.com>
Date:   Sun, 12 Mar 2017 14:34:14 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Mark Brown <broonie@...nel.org>, Michal Hocko <mhocko@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Riley Andrews <riandrews@...roid.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        Rom Lemarchand <romlem@...gle.com>, devel@...verdev.osuosl.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel@...ts.infradead.org,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Brian Starkey <brian.starkey@....com>,
        Daniel Vetter <daniel.vetter@...el.com>, linux-mm@...ck.org
Subject: Re: [RFC PATCH 00/12] Ion cleanup in preparation for moving out of staging

2017-03-09 18:38 GMT+01:00 Laura Abbott <labbott@...hat.com>:
> On 03/09/2017 02:00 AM, Benjamin Gaignard wrote:
>> 2017-03-06 17:04 GMT+01:00 Daniel Vetter <daniel@...ll.ch>:
>>> On Mon, Mar 06, 2017 at 11:58:05AM +0100, Mark Brown wrote:
>>>> On Mon, Mar 06, 2017 at 11:40:41AM +0100, Daniel Vetter wrote:
>>>>
>>>>> No one gave a thing about android in upstream, so Greg KH just dumped it
>>>>> all into staging/android/. We've discussed ION a bunch of times, recorded
>>>>> anything we'd like to fix in staging/android/TODO, and Laura's patch
>>>>> series here addresses a big chunk of that.
>>>>
>>>>> This is pretty much the same approach we (gpu folks) used to de-stage the
>>>>> syncpt stuff.
>>>>
>>>> Well, there's also the fact that quite a few people have issues with the
>>>> design (like Laurent).  It seems like a lot of them have either got more
>>>> comfortable with it over time, or at least not managed to come up with
>>>> any better ideas in the meantime.
>>>
>>> See the TODO, it has everything a really big group (look at the patch for
>>> the full Cc: list) figured needs to be improved at LPC 2015. We don't just
>>> merge stuff because merging stuff is fun :-)
>>>
>>> Laurent was even in that group ...
>>> -Daniel
>>
>> For me those patches are going in the right direction.
>>
>> I still have few questions:
>> - since alignment management has been remove from ion-core, should it
>> be also removed from ioctl structure ?
>
> Yes, I think I'm going to go with the suggestion to fixup the ABI
> so we don't need the compat layer and as part of that I'm also
> dropping the align argument.
>
>> - can you we ride off ion_handle (at least in userland) and only
>> export a dma-buf descriptor ?
>
> Yes, I think this is the right direction given we're breaking
> everything anyway. I was debating trying to keep the two but
> moving to only dma bufs is probably cleaner. The only reason
> I could see for keeping the handles is running out of file
> descriptors for dma-bufs but that seems unlikely.
>>
>> In the future how can we add new heaps ?
>> Some platforms have very specific memory allocation
>> requirements (just have a look in the number of gem custom allocator in drm)
>> Do you plan to add heap type/mask for each ?
>
> Yes, that was my thinking.

My concern is about the policy to adding heaps, will you accept
"customs" heap per
platforms ? per devices ? or only generic ones ?
If you are too strict, we will have lot of out-of-tree heaps and if
you accept of of them
it will be a nightmare to maintain....

Another point is how can we put secure rules (like selinux policy) on
heaps since all the allocations
go to the same device (/dev/ion) ? For example, until now, in Android
we have to give the same
access rights to all the process that use ION.
It will become problem when we will add secure heaps because we won't
be able to distinguish secure
processes to standard ones or set specific policy per heaps.
Maybe I'm wrong here but I have never see selinux policy checking an
ioctl field but if that
exist it could be a solution.

>
>>
>> Benjamin
>>
>
> Thanks,
> Laura
>