On Tue, Apr 28, 2020 at 2:46 PM Peter Collingbourne <pcc@xxxxxxxxxx> wrote:
>
> Render nodes are not just useful for devices supporting GPU hardware
> acceleration. Even on devices that only support dumb frame buffers,
> they are useful in situations where composition (using software
> rasterization) and KMS are done in different processes with buffer
> sharing being used to send frame buffers between them. This is the
> situation on Android, where surfaceflinger is the compositor and the
> composer HAL uses KMS to display the buffers. Thus it is beneficial
> to expose render nodes on all devices that support buffer sharing.
>
> Because all drivers that currently support render nodes also support
> buffer sharing, the DRIVER_RENDER flag is no longer necessary to mark
> devices as supporting render nodes, so remove it and just rely on
> the presence of a prime_handle_to_fd function pointer to determine
> whether buffer sharing is supported.
The idea behind render nodes is that you can freely pass these to
unpriviledged users, and nothing bad happens. That's why we have gpu
reset code in drivers, proper pagetables, and also (in at least the
solid drivers) ban code so that repeat offenders from userspace who
constantly submit endless batch buffers and funny stuff like that
can't DOS the gpu.
Ofc in practice there's hw issues and fun stuff like that sometimes,
and driver bugs, and all that. But that's the aspiration.
Now many of these display-only drivers need contiguous buffers, and
there's not endless amounts of that around. So if you allow random
clients to allocate buffers, they can easily exhaust that, and not
just upset the render side of the gpu, but essentially make it
impossible for a compositor to allocate more framebuffers. I don't
think that's a good idea.
I know there's hw like vc4 which needs contiguous buffers for
everything, but that's kinda the places where aspiration falls a bit
short.
So from that pov I'm a rather worried with handing out render rights
to everyone for these display-only buffers. It's not entirely
harmless.
-Daniel
>
> Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx>
> ---
> Documentation/gpu/drm-uapi.rst | 9 +++++----
> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 2 +-
> drivers/gpu/drm/drm_drv.c | 2 +-
> drivers/gpu/drm/etnaviv/etnaviv_drv.c | 2 +-
> drivers/gpu/drm/exynos/exynos_drm_drv.c | 2 +-
> drivers/gpu/drm/i915/i915_drv.c | 2 +-
> drivers/gpu/drm/lima/lima_drv.c | 2 +-
> drivers/gpu/drm/msm/msm_drv.c | 1 -
> drivers/gpu/drm/nouveau/nouveau_drm.c | 2 +-
> drivers/gpu/drm/omapdrm/omap_drv.c | 2 +-
> drivers/gpu/drm/panfrost/panfrost_drv.c | 2 +-
> drivers/gpu/drm/radeon/radeon_drv.c | 3 +--
> drivers/gpu/drm/tegra/drm.c | 2 +-
> drivers/gpu/drm/v3d/v3d_drv.c | 1 -
> drivers/gpu/drm/vc4/vc4_drv.c | 8 --------
> drivers/gpu/drm/vgem/vgem_drv.c | 2 +-
> drivers/gpu/drm/virtio/virtgpu_drv.c | 2 +-
> drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +-
> include/drm/drm_drv.h | 7 -------
> 19 files changed, 19 insertions(+), 36 deletions(-)
>
> diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst
> index 56fec6ed1ad8..2769714ae75a 100644
> --- a/Documentation/gpu/drm-uapi.rst
> +++ b/Documentation/gpu/drm-uapi.rst
> @@ -129,10 +129,11 @@ authenticate to a DRM-Master prior to getting GPU access. To avoid this
> step and to grant clients GPU access without authenticating, render
> nodes were introduced. Render nodes solely serve render clients, that
> is, no modesetting or privileged ioctls can be issued on render nodes.
> -Only non-global rendering commands are allowed. If a driver supports
> -render nodes, it must advertise it via the DRIVER_RENDER DRM driver
> -capability. If not supported, the primary node must be used for render
> -clients together with the legacy drmAuth authentication procedure.
> +Only non-global rendering commands are allowed. Drivers that support
> +:ref:`PRIME buffer sharing <prime_buffer_sharing>` automatically
> +support render nodes. If a driver does not support render nodes,
> +the primary node must be used for render clients together with the
> +legacy drmAuth authentication procedure.
>
> If a driver advertises render node support, DRM core will create a
> separate render node called renderD<num>. There will be one render node
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 8ea86ffdea0d..46460620bc37 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -1426,7 +1426,7 @@ static struct drm_driver kms_driver = {
> .driver_features =
> DRIVER_ATOMIC |
> DRIVER_GEM |
> - DRIVER_RENDER | DRIVER_MODESET | DRIVER_SYNCOBJ |
> + DRIVER_MODESET | DRIVER_SYNCOBJ |
> DRIVER_SYNCOBJ_TIMELINE,
> .open = amdgpu_driver_open_kms,
> .postclose = amdgpu_driver_postclose_kms,
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 7b1a628d1f6e..8861a30920e5 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -651,7 +651,7 @@ int drm_dev_init(struct drm_device *dev,
> goto err_free;
> }
>
> - if (drm_core_check_feature(dev, DRIVER_RENDER)) {
> + if (driver->prime_handle_to_fd) {
> ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
> if (ret)
> goto err_minors;
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> index a8685b2e1803..abfb143334ac 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> @@ -497,7 +497,7 @@ static const struct file_operations fops = {
> };
>
> static struct drm_driver etnaviv_drm_driver = {
> - .driver_features = DRIVER_GEM | DRIVER_RENDER,
> + .driver_features = DRIVER_GEM,
> .open = etnaviv_open,
> .postclose = etnaviv_postclose,
> .gem_free_object_unlocked = etnaviv_gem_free_object,
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> index 57defeb44522..834eb5713fe4 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> @@ -121,7 +121,7 @@ static const struct file_operations exynos_drm_driver_fops = {
>
> static struct drm_driver exynos_drm_driver = {
> .driver_features = DRIVER_MODESET | DRIVER_GEM
> - | DRIVER_ATOMIC | DRIVER_RENDER,
> + | DRIVER_ATOMIC,
> .open = exynos_drm_open,
> .lastclose = drm_fb_helper_lastclose,
> .postclose = exynos_drm_postclose,
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 81a4621853db..b028a32fcac5 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1834,7 +1834,7 @@ static struct drm_driver driver = {
> */
> .driver_features =
> DRIVER_GEM |
> - DRIVER_RENDER | DRIVER_MODESET | DRIVER_ATOMIC | DRIVER_SYNCOBJ,
> + DRIVER_MODESET | DRIVER_ATOMIC | DRIVER_SYNCOBJ,
> .release = i915_driver_release,
> .open = i915_driver_open,
> .lastclose = i915_driver_lastclose,
> diff --git a/drivers/gpu/drm/lima/lima_drv.c b/drivers/gpu/drm/lima/lima_drv.c
> index 2daac64d8955..bd8b6ad25ac0 100644
> --- a/drivers/gpu/drm/lima/lima_drv.c
> +++ b/drivers/gpu/drm/lima/lima_drv.c
> @@ -252,7 +252,7 @@ DEFINE_DRM_GEM_FOPS(lima_drm_driver_fops);
> */
>
> static struct drm_driver lima_drm_driver = {
> - .driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ,
> + .driver_features = DRIVER_GEM | DRIVER_SYNCOBJ,
> .open = lima_drm_driver_open,
> .postclose = lima_drm_driver_postclose,
> .ioctls = lima_drm_driver_ioctls,
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 29295dee2a2e..061e62d4b691 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -1000,7 +1000,6 @@ static const struct file_operations fops = {
>
> static struct drm_driver msm_driver = {
> .driver_features = DRIVER_GEM |
> - DRIVER_RENDER |
> DRIVER_ATOMIC |
> DRIVER_MODESET,
> .open = msm_open,
> diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
> index ca4087f5a15b..3ba8c9789292 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_drm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
> @@ -1169,7 +1169,7 @@ nouveau_driver_fops = {
> static struct drm_driver
> driver_stub = {
> .driver_features =
> - DRIVER_GEM | DRIVER_MODESET | DRIVER_RENDER
> + DRIVER_GEM | DRIVER_MODESET
> #if defined(CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT)
> | DRIVER_KMS_LEGACY_CONTEXT
> #endif
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> index cdafd7ef1c32..fe25b352a755 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> @@ -558,7 +558,7 @@ static const struct file_operations omapdriver_fops = {
>
> static struct drm_driver omap_drm_driver = {
> .driver_features = DRIVER_MODESET | DRIVER_GEM |
> - DRIVER_ATOMIC | DRIVER_RENDER,
> + DRIVER_ATOMIC,
> .open = dev_open,
> .lastclose = drm_fb_helper_lastclose,
> #ifdef CONFIG_DEBUG_FS
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 882fecc33fdb..058765d5d5d5 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -550,7 +550,7 @@ DEFINE_DRM_GEM_FOPS(panfrost_drm_driver_fops);
> * - 1.1 - adds HEAP and NOEXEC flags for CREATE_BO
> */
> static struct drm_driver panfrost_drm_driver = {
> - .driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ,
> + .driver_features = DRIVER_GEM | DRIVER_SYNCOBJ,
> .open = panfrost_open,
> .postclose = panfrost_postclose,
> .ioctls = panfrost_drm_driver_ioctls,
> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
> index 59f8186a2415..9457b2f8f81e 100644
> --- a/drivers/gpu/drm/radeon/radeon_drv.c
> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
> @@ -600,8 +600,7 @@ static const struct file_operations radeon_driver_kms_fops = {
> };
>
> static struct drm_driver kms_driver = {
> - .driver_features =
> - DRIVER_GEM | DRIVER_RENDER,
> + .driver_features = DRIVER_GEM,
> .load = radeon_driver_load_kms,
> .open = radeon_driver_open_kms,
> .postclose = radeon_driver_postclose_kms,
> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> index bd268028fb3d..55190c582946 100644
> --- a/drivers/gpu/drm/tegra/drm.c
> +++ b/drivers/gpu/drm/tegra/drm.c
> @@ -849,7 +849,7 @@ static int tegra_debugfs_init(struct drm_minor *minor)
>
> static struct drm_driver tegra_drm_driver = {
> .driver_features = DRIVER_MODESET | DRIVER_GEM |
> - DRIVER_ATOMIC | DRIVER_RENDER,
> + DRIVER_ATOMIC,
> .open = tegra_drm_open,
> .postclose = tegra_drm_postclose,
> .lastclose = drm_fb_helper_lastclose,
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.c b/drivers/gpu/drm/v3d/v3d_drv.c
> index eaa8e9682373..96db702fd648 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.c
> +++ b/drivers/gpu/drm/v3d/v3d_drv.c
> @@ -195,7 +195,6 @@ static const struct drm_ioctl_desc v3d_drm_ioctls[] = {
>
> static struct drm_driver v3d_drm_driver = {
> .driver_features = (DRIVER_GEM |
> - DRIVER_RENDER |
> DRIVER_SYNCOBJ),
>
> .open = v3d_open,
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
> index 76f93b662766..bf143d1e0d2e 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.c
> +++ b/drivers/gpu/drm/vc4/vc4_drv.c
> @@ -181,7 +181,6 @@ static struct drm_driver vc4_drm_driver = {
> .driver_features = (DRIVER_MODESET |
> DRIVER_ATOMIC |
> DRIVER_GEM |
> - DRIVER_RENDER |
> DRIVER_SYNCOBJ),
> .open = vc4_open,
> .postclose = vc4_close,
> @@ -251,7 +250,6 @@ static int vc4_drm_bind(struct device *dev)
> struct platform_device *pdev = to_platform_device(dev);
> struct drm_device *drm;
> struct vc4_dev *vc4;
> - struct device_node *node;
> int ret = 0;
>
> dev->coherent_dma_mask = DMA_BIT_MASK(32);
> @@ -260,12 +258,6 @@ static int vc4_drm_bind(struct device *dev)
> if (!vc4)
> return -ENOMEM;
>
> - /* If VC4 V3D is missing, don't advertise render nodes. */
> - node = of_find_matching_node_and_match(NULL, vc4_v3d_dt_match, NULL);
> - if (!node || !of_device_is_available(node))
> - vc4_drm_driver.driver_features &= ~DRIVER_RENDER;
> - of_node_put(node);
> -
> drm = drm_dev_alloc(&vc4_drm_driver, dev);
> if (IS_ERR(drm))
> return PTR_ERR(drm);
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index 909eba43664a..abc7345a2e96 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -437,7 +437,7 @@ static void vgem_release(struct drm_device *dev)
> }
>
> static struct drm_driver vgem_driver = {
> - .driver_features = DRIVER_GEM | DRIVER_RENDER,
> + .driver_features = DRIVER_GEM,
> .release = vgem_release,
> .open = vgem_open,
> .postclose = vgem_postclose,
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index ab4bed78e656..22195e008f0d 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -189,7 +189,7 @@ MODULE_AUTHOR("Alon Levy");
> DEFINE_DRM_GEM_FOPS(virtio_gpu_driver_fops);
>
> static struct drm_driver driver = {
> - .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_RENDER | DRIVER_ATOMIC,
> + .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
> .open = virtio_gpu_driver_open,
> .postclose = virtio_gpu_driver_postclose,
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index c2247a893ed4..415c3f8ea907 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -1435,7 +1435,7 @@ static const struct file_operations vmwgfx_driver_fops = {
>
> static struct drm_driver driver = {
> .driver_features =
> - DRIVER_MODESET | DRIVER_RENDER | DRIVER_ATOMIC,
> + DRIVER_MODESET | DRIVER_ATOMIC,
> .ioctls = vmw_ioctls,
> .num_ioctls = ARRAY_SIZE(vmw_ioctls),
> .master_set = vmw_master_set,
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 97109df5beac..f0277d3f89fe 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -61,13 +61,6 @@ enum drm_driver_feature {
> * Driver supports mode setting interfaces (KMS).
> */
> DRIVER_MODESET = BIT(1),
> - /**
> - * @DRIVER_RENDER:
> - *
> - * Driver supports dedicated render nodes. See also the :ref:`section on
> - * render nodes <drm_render_node>` for details.
> - */
> - DRIVER_RENDER = BIT(3),
> /**
> * @DRIVER_ATOMIC:
> *
> --
> 2.26.2.303.gf8c07b1a785-goog
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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