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From: Inki Dae <inki.dae@samsung.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Kyungmin Park <kyungmin.park@samsung.com>,
	Jerome Glisse <jglisse@redhat.com>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH] exynos: Put a stop to the userptr heresy.
Date: Thu, 10 Jul 2014 00:39:24 +0900	[thread overview]
Message-ID: <53BD622C.9050000@samsung.com> (raw)
In-Reply-To: <CAKMK7uH2-ZU9QMXyUGREqcToB0ds_gTsG-iSyOJ24nDyy3NgxA@mail.gmail.com>

On 2014년 07월 09일 18:23, Daniel Vetter wrote:
> On Tue, Jul 8, 2014 at 6:20 PM, Inki Dae <inki.dae@samsung.com> wrote:
>> 2014-07-08 22:37 GMT+09:00 Daniel Vetter <daniel@ffwll.ch>:
>>> On Wed, Jul 02, 2014 at 11:25:19AM -0400, Jerome Glisse wrote:
>>>> Anyway as this is upstream i guess you can keep it. This is just an horrible
>>>> API that allow to circumvant any limit set by memcg for page locking and all.
>>>> But anyway GPU driver never played in the same ballpark as other driver.
>>>
>>> I agree that exynos userptr as-is should be removed since as opposed to
>>> the i915 implementation it doesn't play nice with the core mm
>>
>> Can you give me more details why you think so?
> 
>>From a very quick look there's two pieces:
> - The implementation with the vma tricks looks _really_ scary. You'd
> need to have Al Viro's opinion on it though.

You mean that it checks VM_DONTCOPY flag before copying vma? If so, I
really forgot it.

> - If I'm reading the code correctly userspace can pin unlimted amounts
> of memory, but I've gotten a bit lost in the code. In i915 we have

Not so. g2d driver is checking if user-requested buffer size is more
than maximum capacity of g2d dma. So it can never pin unlimited amounts
of memory.

> shrinkers and mmu notifier to make sure that if the vm needs this
> memory again we'll make it available.

I am not familiar to mmu notifier. I will look into how i915 driver
handle it.

Thanks for comments,
Inki Dae

> -Daniel
> 

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  reply	other threads:[~2014-07-09 15:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-30 21:46 [PATCH] exynos: Put a stop to the userptr heresy j.glisse
2014-07-01  8:55 ` Inki Dae
2014-07-01 15:03   ` Jerome Glisse
2014-07-02 15:09     ` Inki Dae
2014-07-02 15:25       ` Jerome Glisse
2014-07-08 13:37         ` Daniel Vetter
2014-07-08 16:20           ` Inki Dae
2014-07-09  9:23             ` Daniel Vetter
2014-07-09 15:39               ` Inki Dae [this message]
2014-07-10  7:11                 ` Daniel Vetter

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