From: Christoph Hellwig <hch@infradead.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Christoph Hellwig <hch@infradead.org>,
Oleksandr Andrushchenko <andr2000@gmail.com>,
Juergen Gross <jgross@suse.com>,
Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Daniel Vetter <daniel.vetter@intel.com>,
xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com
Subject: Re: [PATCH] drm/xen-front: Make shmem backed display buffer coherent
Date: Thu, 20 Dec 2018 10:38:51 -0800 [thread overview]
Message-ID: <20181220183851.GA27025@infradead.org> (raw)
In-Reply-To: <CAKMK7uFxU9Q5u9TxxHqAgFZuQFCFDvxWHDtRLiQf+3hu_4jPcQ@mail.gmail.com>
On Thu, Dec 20, 2018 at 07:35:15PM +0100, Daniel Vetter wrote:
> > Err, with streaming DMA buffer sharing is trivial. The coherent DMA
> > allocator is what causes all kinds of horrible hacks that can't actually
> > work on various platforms.
>
> Hm, I thought the streaming dma api is the one that causes bounce
> buffers and all that fun. If you're unlucky at least.
Yes it may. But even if that happens everything will actually work,
just slower. While the dma coherent API is simply broken.
But if you don't want bounce buffering you need to use the dma
noncoherent allocator as proposed here:
https://lists.linuxfoundation.org/pipermail/iommu/2018-December/031982.html
which combines allocating memory that doesn't need to be bounce
buffered with a sharing scheme that can actually work.
next prev parent reply other threads:[~2018-12-20 18:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 10:32 [PATCH] drm/xen-front: Make shmem backed display buffer coherent Oleksandr Andrushchenko
2018-12-13 10:17 ` Oleksandr Andrushchenko
2018-12-13 15:48 ` Daniel Vetter
2018-12-14 7:09 ` Oleksandr Andrushchenko
2018-12-14 8:35 ` Daniel Vetter
2018-12-17 8:03 ` Oleksandr Andrushchenko
2018-12-18 19:20 ` Noralf Trønnes
2018-12-19 8:18 ` Oleksandr Andrushchenko
2018-12-19 13:14 ` Gerd Hoffmann
2018-12-19 13:21 ` Oleksandr Andrushchenko
2018-12-19 14:10 ` Gerd Hoffmann
2018-12-20 11:19 ` Oleksandr Andrushchenko
2018-12-20 15:37 ` Christoph Hellwig
2018-12-19 16:14 ` Noralf Trønnes
2018-12-20 11:24 ` Oleksandr Andrushchenko
2018-12-20 15:36 ` Christoph Hellwig
2018-12-20 15:49 ` Oleksandr Andrushchenko
2018-12-20 17:39 ` Christoph Hellwig
2018-12-20 18:29 ` Daniel Vetter
2018-12-20 18:33 ` Christoph Hellwig
2018-12-20 18:35 ` Daniel Vetter
2018-12-20 18:38 ` Christoph Hellwig [this message]
2018-12-21 9:16 ` Oleksandr Andrushchenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181220183851.GA27025@infradead.org \
--to=hch@infradead.org \
--cc=andr2000@gmail.com \
--cc=boris.ostrovsky@oracle.com \
--cc=daniel.vetter@intel.com \
--cc=daniel@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=jgross@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=oleksandr_andrushchenko@epam.com \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox