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drm/virtio: Fix handling CONFIG_DRM_VIRTIO_GPU_KMS option

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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 <kraxel@redhat.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Fixes: 72122c69d7 ("drm/virtio: Add option to disable KMS support")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230306163916.1595961-1-dmitry.osipenko@collabora.com
This commit is contained in:
Dmitry Osipenko
2023-03-06 19:39:16 +03:00
parent bf458e5b13
commit aad9729ec0
1 changed files with 10 additions and 8 deletions
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18
drivers/gpu/drm/virtio/virtgpu_kms.c
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@@ -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,