From: Rob Clark <robdcl...@chromium.org> Add a build option to disable modesetting support. This is useful in cases where the guest only needs to use the GPU in a headless mode, or (such as in the CrOS usage) window surfaces are proxied to a host compositor.
As the modesetting ioctls are a big surface area for potential security bugs to be found (it's happened in the past, we should assume it will again in the future), it makes sense to have a build option to disable those ioctls in cases where they serve no legitimate purpose. v2: Use more if (IS_ENABLED(...)) v3: Also permit the host to advertise no scanouts v4: Spiff out commit msg v5: Make num_scanouts==0 and DRM_VIRTIO_GPU_KMS=n behave the same v6: Drop conditionally building virtgpu_display.c and early-out of it's init/fini fxns instead Signed-off-by: Rob Clark <robdcl...@chromium.org> Reviewed-by: Dmitry Osipenko <dmitry.osipe...@collabora.com> Reviewed-by: Javier Martinez Canillas <javi...@redhat.com> --- drivers/gpu/drm/virtio/Kconfig | 11 +++++++++++ drivers/gpu/drm/virtio/virtgpu_display.c | 6 ++++++ drivers/gpu/drm/virtio/virtgpu_drv.c | 4 ++++ drivers/gpu/drm/virtio/virtgpu_kms.c | 23 ++++++++++++++--------- 4 files changed, 35 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/virtio/Kconfig b/drivers/gpu/drm/virtio/Kconfig index 51ec7c3240c9..ea06ff2aa4b4 100644 --- a/drivers/gpu/drm/virtio/Kconfig +++ b/drivers/gpu/drm/virtio/Kconfig @@ -11,3 +11,14 @@ config DRM_VIRTIO_GPU QEMU based VMMs (like KVM or Xen). If unsure say M. + +config DRM_VIRTIO_GPU_KMS + bool "Virtio GPU driver modesetting support" + depends on DRM_VIRTIO_GPU + default y + help + Enable modesetting support for virtio GPU driver. This can be + disabled in cases where only "headless" usage of the GPU is + required. + + If unsure, say Y. diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c b/drivers/gpu/drm/virtio/virtgpu_display.c index 9ea7611a9e0f..ad924a8502e9 100644 --- a/drivers/gpu/drm/virtio/virtgpu_display.c +++ b/drivers/gpu/drm/virtio/virtgpu_display.c @@ -336,6 +336,9 @@ int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev) { int i, ret; + if (!vgdev->num_scanouts) + return 0; + ret = drmm_mode_config_init(vgdev->ddev); if (ret) return ret; @@ -362,6 +365,9 @@ void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev) { int i; + if (!vgdev->num_scanouts) + return; + for (i = 0 ; i < vgdev->num_scanouts; ++i) kfree(vgdev->outputs[i].edid); } diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c index ae97b98750b6..add075681e18 100644 --- a/drivers/gpu/drm/virtio/virtgpu_drv.c +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c @@ -172,6 +172,10 @@ MODULE_AUTHOR("Alon Levy"); DEFINE_DRM_GEM_FOPS(virtio_gpu_driver_fops); static const struct drm_driver driver = { + /* + * If KMS is disabled DRIVER_MODESET and DRIVER_ATOMIC are masked + * out via drm_device::driver_features: + */ .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_RENDER | DRIVER_ATOMIC, .open = virtio_gpu_driver_open, .postclose = virtio_gpu_driver_postclose, diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c index 27b7f14dae89..02e5c18c2c75 100644 --- a/drivers/gpu/drm/virtio/virtgpu_kms.c +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c @@ -223,12 +223,15 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev) num_scanouts, &num_scanouts); vgdev->num_scanouts = min_t(uint32_t, num_scanouts, VIRTIO_GPU_MAX_SCANOUTS); - if (!vgdev->num_scanouts) { - DRM_ERROR("num_scanouts is zero\n"); - ret = -EINVAL; - goto err_scanouts; + + if (IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS) || !vgdev->num_scanouts) { + DRM_INFO("KMS disabled\n"); + vgdev->num_scanouts = 0; + vgdev->has_edid = false; + dev->driver_features &= ~(DRIVER_MODESET | DRIVER_ATOMIC); + } else { + DRM_INFO("number of scanouts: %d\n", num_scanouts); } - DRM_INFO("number of scanouts: %d\n", num_scanouts); virtio_cread_le(vgdev->vdev, struct virtio_gpu_config, num_capsets, &num_capsets); @@ -246,10 +249,12 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev) virtio_gpu_get_capsets(vgdev, num_capsets); if (vgdev->has_edid) virtio_gpu_cmd_get_edids(vgdev); - virtio_gpu_cmd_get_display_info(vgdev); - virtio_gpu_notify(vgdev); - wait_event_timeout(vgdev->resp_wq, !vgdev->display_info_pending, - 5 * HZ); + if (vgdev->num_scanouts) { + virtio_gpu_cmd_get_display_info(vgdev); + virtio_gpu_notify(vgdev); + wait_event_timeout(vgdev->resp_wq, !vgdev->display_info_pending, + 5 * HZ); + } return 0; err_scanouts: -- 2.39.1