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    SubjectRe: [PATCH v2] drm/virtio: Fix handling CONFIG_DRM_VIRTIO_GPU_KMS option
    On 2023/03/06, Dmitry Osipenko wrote:
    > 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.
    >
    > Fixes: 72122c69d717 ("drm/virtio: Add option to disable KMS support")
    > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
    > ---
    >
    > Changelog:
    >
    > v2: - Moved the "has_edid" under the "num_scanouts" condition, like was
    > suggested by Gerd Hoffmann.
    >

    Hi Dmitry, I think there's more than one piece like that in the driver.

    > drivers/gpu/drm/virtio/virtgpu_kms.c | 14 ++++++++------
    > 1 file changed, 8 insertions(+), 6 deletions(-)
    >
    > diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
    > index 874ad6c2621a..15f2519988e7 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);

    Worth doing the same thing in virtio_gpu_init()? Aka move the has_edid
    && get_edids within the num_scanouts if block.

    HTH
    Emil

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