From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Stevens <stevensd@chromium.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Jason Wang <jasowang@redhat.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
open list <linux-kernel@vger.kernel.org>,
ML dri-devel <dri-devel@lists.freedesktop.org>,
"open list:VIRTIO GPU DRIVER"
<virtualization@lists.linux-foundation.org>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
"moderated list:DMA BUFFER SHARING FRAMEWORK"
<linaro-mm-sig@lists.linaro.org>,
virtio-dev@lists.oasis-open.org
Subject: Re: [PATCH v3 4/4] drm/virtio: Support virtgpu exported resources
Date: Mon, 8 Jun 2020 11:17:18 -0400 [thread overview]
Message-ID: <20200608111647-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAD=HUj6kF2JFyC9c0CY5_f-cv6r97501Z2f8D9x0VhQpRen+bw@mail.gmail.com>
On Mon, Jun 08, 2020 at 07:36:55PM +0900, David Stevens wrote:
> On Mon, Jun 8, 2020 at 6:43 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Fri, May 15, 2020 at 04:26:15PM +0900, David Stevens wrote:
> > > > > + if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_RESOURCE_UUID)) {
> > > > > + vgdev->has_resource_assign_uuid = true;
> > > > > + }
> > > >
> > > >
> > > > Just a question: this relies on DMA bufs so I assume it is
> > > > not really assumed to work when DMA API is bypassed, right?
> > > > Rather than worry what does it mean, how about just
> > > > disabling this feature without PLATFORM_DMA for now?
> > >
> > > By PLATFORM_DMA, do you mean CONFIG_DMA_SHARED_BUFFER?
> >
> > Sorry, no. I mean VIRTIO_F_IOMMU_PLATFORM which in the
> > future will be renamed to VIRTIO_F_PLATFORM_ACCESS.
>
> Shouldn't things work independent of whether or not that feature is
> set? If a virtio driver properly uses the dma_buf APIs (which virtgpu
> seems to), then that should take care of any mapping/synchronization
> related to VIRTIO_F_IOMMU_PLATFORM. If anything, the case where
> VIRTIO_F_IOMMU_PLATFORM isn't set is easier, since then we know that
> the "the device has same access [sic] to memory addresses supplied to
> it as the driver has", according to the specification.
>
> -David
I don't know much about drm so I can't tell, I was hoping Gerd can
explain.
--
MST
next prev parent reply other threads:[~2020-06-08 15:17 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-11 11:20 [PATCH v3 0/4] Support virtio cross-device resources David Stevens
2020-03-11 11:20 ` [PATCH v3 1/4] dma-buf: add support for virtio exported objects David Stevens
2020-05-13 15:45 ` Daniel Vetter
2020-05-14 2:08 ` David Stevens
2020-05-14 12:28 ` Daniel Vetter
2020-05-14 7:59 ` Gerd Hoffmann
2020-05-14 12:31 ` Daniel Vetter
2020-05-14 8:19 ` David Stevens
2020-05-14 12:30 ` Daniel Vetter
2020-05-15 5:07 ` David Stevens
2020-05-15 14:03 ` Daniel Vetter
2020-05-18 11:17 ` Sumit Semwal
2020-03-11 11:20 ` [PATCH v3 2/4] drm/prime: " David Stevens
2020-03-11 11:20 ` [PATCH v3 3/4] virtio-gpu: add VIRTIO_GPU_F_RESOURCE_UUID feature David Stevens
2020-03-11 11:20 ` [PATCH v3 4/4] drm/virtio: Support virtgpu exported resources David Stevens
2020-05-13 16:34 ` Michael S. Tsirkin
2020-05-15 7:26 ` David Stevens
2020-06-08 9:43 ` Michael S. Tsirkin
2020-06-08 10:36 ` David Stevens
2020-06-08 15:17 ` Michael S. Tsirkin [this message]
2020-03-20 6:48 ` [PATCH v3 0/4] Support virtio cross-device resources Gerd Hoffmann
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