| Message ID | 20230306143234.1561759-1-dmitry.osipenko@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/virtio: Fix handling CONFIG_DRM_VIRTIO_GPU_KMS option | expand |
On Mon, Mar 06, 2023 at 05:32:34PM +0300, 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. Acked-by: Gerd Hoffmann <kraxel@redhat.com>
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
On 3/6/23 18:02, Emil Velikov wrote: > 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. Good catch, that could be done for consistency.
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); + 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;
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. drivers/gpu/drm/virtio/virtgpu_kms.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)