From: Gerd Hoffmann <kraxel@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>,
Emil Velikov <emil.l.velikov@gmail.com>,
Sean Paul <sean@poorly.run>,
dri-devel <dri-devel@lists.freedesktop.org>,
Sam Ravnborg <sam@ravnborg.org>
Subject: Re: [PATCH 1/2] drm/shmem: Use cached mappings by default
Date: Mon, 18 May 2020 12:11:32 +0200 [thread overview]
Message-ID: <20200518101132.ves2qswskaiajh2y@sirius.home.kraxel.org> (raw)
In-Reply-To: <3bc1a032-2e7a-d7a8-e5e6-8d53a9e9bd3a@suse.de>
On Mon, May 18, 2020 at 10:50:15AM +0200, Thomas Zimmermann wrote:
> Hi Gerd
>
> Am 18.05.20 um 10:23 schrieb Gerd Hoffmann:
> >>> $ git grep drm_gem_shmem_mmap
> >>>
> >>> We also need correct access from userspace, otherwise the gpu is going to
> >>> be sad.
> >>
> >> I've been thinking about this, and I think it means that we can never
> >> have cached mappings anywhere. Even if shmem supports it internally for
> >> most drivers, as soon as the page are exported, the importer could
> >> expect uncached memory.
> >
> > The importer should not expect anything but call dma-buf ops so the
> > exporter has a chance to handle this correctly.
>
> I have the following case in mind: Suppose the exporter maps cached
> pages and the importer expects uncached pages for DMA. There is
> map_dma_buf/unmap_dma_buf, which can implement a cache flush for the
> cached pages. Is it guaranteed that the importer calls this around each
> DMA operation?
I think the importer is supposed to do that, but I wouldn't surprised if
there are cases in tree where this isn't implemented correctly ...
take care,
Gerd
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2020-05-18 10:11 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 15:03 [PATCH 0/2] Default to cachable mappings for GEM SHMEM Thomas Zimmermann
2020-05-13 15:03 ` [PATCH 1/2] drm/shmem: Use cached mappings by default Thomas Zimmermann
2020-05-13 15:06 ` Thomas Zimmermann
2020-05-14 12:40 ` Daniel Vetter
2020-05-14 15:27 ` Thomas Zimmermann
2020-05-14 20:36 ` Rob Herring
2020-05-15 6:58 ` Thomas Zimmermann
2020-05-15 14:10 ` Daniel Vetter
2020-05-18 8:13 ` Thomas Zimmermann
2020-05-18 8:23 ` Gerd Hoffmann
2020-05-18 8:50 ` Thomas Zimmermann
2020-05-18 10:11 ` Gerd Hoffmann [this message]
2020-05-18 14:40 ` Daniel Vetter
2020-05-19 6:31 ` Thomas Zimmermann
2020-05-13 15:03 ` [PATCH 2/2] drm/udl: Use GEM vmap/mmap function from SHMEM helpers Thomas Zimmermann
2020-05-13 15:49 ` Daniel Vetter
2020-05-13 17:19 ` Thomas Zimmermann
2020-05-14 12:44 ` Daniel Vetter
2020-05-19 6:36 ` Thomas Zimmermann
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=20200518101132.ves2qswskaiajh2y@sirius.home.kraxel.org \
--to=kraxel@redhat.com \
--cc=airlied@linux.ie \
--cc=dri-devel@lists.freedesktop.org \
--cc=emil.l.velikov@gmail.com \
--cc=sam@ravnborg.org \
--cc=sean@poorly.run \
--cc=tzimmermann@suse.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.