linux-kernel - Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190725140548.GB25010@infradead.org>
Date:   Thu, 25 Jul 2019 07:05:48 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     "Andrew F. Davis" <afd@...com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Laura Abbott <labbott@...hat.com>,
        John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Vincent Donnefort <Vincent.Donnefort@....com>,
        Sudipto Paul <Sudipto.Paul@....com>,
        Xu YiPing <xuyiping@...ilicon.com>,
        "Chenfeng (puck)" <puck.chen@...ilicon.com>,
        butao <butao@...ilicon.com>,
        "Xiaqing (A)" <saberlily.xia@...ilicon.com>,
        Yudongbin <yudongbin@...ilicon.com>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps

On Thu, Jul 25, 2019 at 09:47:11AM -0400, Andrew F. Davis wrote:
> This is a central allocator, it is not tied to any one device. If we
> knew the one device ahead of time we would just use the existing dma_alloc.
> 
> We might be able to solve some of that with late mapping after all the
> devices attach to the buffer, but even then, which device's CMA area
> would we chose to use from all the attached devices?
> 
> I can agree that allocating from per-device CMA using Heaps doesn't make
> much sense, but for global pools I'm not sure I see any way to allow
> devices to select which pool is right for a specific use. They don't
> have the full use-case information like the application does, the
> selection needs to be made from the application.

Well, the examples we had before was that we clear want to use the
per-device CMA area.  And at least in upstream a CMA area either is
global or attached to a device, as we otherwise wouldn't find it.