From 72122c69d71784e390527819754ea456421c4501 Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Thu, 2 Mar 2023 15:35:06 -0800 Subject: drm/virtio: Add option to disable KMS support 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 Reviewed-by: Dmitry Osipenko Reviewed-by: Javier Martinez Canillas Reviewed-by: Gerd Hoffmann Signed-off-by: Dmitry Osipenko Link: https://patchwork.freedesktop.org/patch/msgid/20230302233506.3146290-1-robdclark@gmail.com --- drivers/gpu/drm/virtio/virtgpu_kms.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) (limited to 'drivers/gpu/drm/virtio/virtgpu_kms.c') 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: -- cgit From aad9729ec0e009440ac8c1a4be2204e4d3c08977 Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko Date: Mon, 6 Mar 2023 19:39:16 +0300 Subject: drm/virtio: Fix handling CONFIG_DRM_VIRTIO_GPU_KMS option VirtIO-GPU got a new config option for disabling KMS. There were two problems left unnoticed during review when the new option was added: 1. The IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS) check in the code was inverted, hence KMS was disabled when it should be enabled and vice versa. 2. The disabled KMS crashed kernel with a NULL dereference in drm_kms_helper_hotplug_event(), which shall not be invoked with a disabled KMS. Fix the inverted config option check in the code and skip handling the VIRTIO_GPU_EVENT_DISPLAY sent by host when KMS is disabled in guest to fix the crash. Acked-by: Gerd Hoffmann Reviewed-by: Emil Velikov Fixes: 72122c69d717 ("drm/virtio: Add option to disable KMS support") Signed-off-by: Dmitry Osipenko Link: https://patchwork.freedesktop.org/patch/msgid/20230306163916.1595961-1-dmitry.osipenko@collabora.com --- drivers/gpu/drm/virtio/virtgpu_kms.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'drivers/gpu/drm/virtio/virtgpu_kms.c') diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c index 02e5c18c2c75..5a3b5aaed1f3 100644 --- a/drivers/gpu/drm/virtio/virtgpu_kms.c +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c @@ -43,11 +43,13 @@ static void virtio_gpu_config_changed_work_func(struct work_struct *work) virtio_cread_le(vgdev->vdev, struct virtio_gpu_config, events_read, &events_read); if (events_read & VIRTIO_GPU_EVENT_DISPLAY) { - if (vgdev->has_edid) - virtio_gpu_cmd_get_edids(vgdev); - virtio_gpu_cmd_get_display_info(vgdev); - virtio_gpu_notify(vgdev); - drm_helper_hpd_irq_event(vgdev->ddev); + if (vgdev->num_scanouts) { + if (vgdev->has_edid) + virtio_gpu_cmd_get_edids(vgdev); + virtio_gpu_cmd_get_display_info(vgdev); + virtio_gpu_notify(vgdev); + drm_helper_hpd_irq_event(vgdev->ddev); + } events_clear |= VIRTIO_GPU_EVENT_DISPLAY; } virtio_cwrite_le(vgdev->vdev, struct virtio_gpu_config, @@ -224,7 +226,7 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev) vgdev->num_scanouts = min_t(uint32_t, num_scanouts, VIRTIO_GPU_MAX_SCANOUTS); - if (IS_ENABLED(CONFIG_DRM_VIRTIO_GPU_KMS) || !vgdev->num_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; @@ -247,9 +249,9 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev) if (num_capsets) virtio_gpu_get_capsets(vgdev, num_capsets); - if (vgdev->has_edid) - virtio_gpu_cmd_get_edids(vgdev); if (vgdev->num_scanouts) { + 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, -- cgit