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Message-Id: <20230301185432.3010939-1-robdclark@gmail.com>
Date: Wed, 1 Mar 2023 10:54:32 -0800
From: Rob Clark <robdclark@...il.com>
To: dri-devel@...ts.freedesktop.org
Cc: Chia-I Wu <olvaffe@...il.com>, Ryan Neph <ryanneph@...omium.org>,
Dmitry Osipenko <dmitry.osipenko@...labora.com>,
Gerd Hoffmann <kraxel@...hat.com>,
Daniel Vetter <daniel@...ll.ch>,
Rob Clark <robdclark@...omium.org>,
Javier Martinez Canillas <javierm@...hat.com>,
David Airlie <airlied@...hat.com>,
Gurchetan Singh <gurchetansingh@...omium.org>,
virtualization@...ts.linux-foundation.org (open list:VIRTIO GPU DRIVER),
linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v5] drm/virtio: Add option to disable KMS support
From: Rob Clark <robdclark@...omium.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
Signed-off-by: Rob Clark <robdclark@...omium.org>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>
---
drivers/gpu/drm/virtio/Kconfig | 11 ++++++++++
drivers/gpu/drm/virtio/Makefile | 5 ++++-
drivers/gpu/drm/virtio/virtgpu_drv.c | 4 ++++
drivers/gpu/drm/virtio/virtgpu_drv.h | 10 +++++++++
drivers/gpu/drm/virtio/virtgpu_kms.c | 33 +++++++++++++++++-----------
5 files changed, 49 insertions(+), 14 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/Makefile b/drivers/gpu/drm/virtio/Makefile
index b99fa4a73b68..24c7ebe87032 100644
--- a/drivers/gpu/drm/virtio/Makefile
+++ b/drivers/gpu/drm/virtio/Makefile
@@ -4,8 +4,11 @@
# Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
virtio-gpu-y := virtgpu_drv.o virtgpu_kms.o virtgpu_gem.o virtgpu_vram.o \
- virtgpu_display.o virtgpu_vq.o \
+ virtgpu_vq.o \
virtgpu_fence.o virtgpu_object.o virtgpu_debugfs.o virtgpu_plane.o \
virtgpu_ioctl.o virtgpu_prime.o virtgpu_trace_points.o
+virtio-gpu-$(CONFIG_DRM_VIRTIO_GPU_KMS) += \
+ virtgpu_display.o
+
obj-$(CONFIG_DRM_VIRTIO_GPU) += virtio-gpu.o
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_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index af6ffb696086..ffe8faf67247 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -426,8 +426,18 @@ virtio_gpu_cmd_set_scanout_blob(struct virtio_gpu_device *vgdev,
uint32_t x, uint32_t y);
/* virtgpu_display.c */
+#if defined(CONFIG_DRM_VIRTIO_GPU_KMS)
int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev);
void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev);
+#else
+static inline int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev)
+{
+ return 0;
+}
+static inline void virtio_gpu_modeset_fini(struct virtio_gpu_device *vgdev)
+{
+}
+#endif
/* virtgpu_plane.c */
uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc);
diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
index 27b7f14dae89..61a1afe2c8c8 100644
--- a/drivers/gpu/drm/virtio/virtgpu_kms.c
+++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
@@ -223,21 +223,26 @@ 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);
DRM_INFO("number of cap sets: %d\n", num_capsets);
- ret = virtio_gpu_modeset_init(vgdev);
- if (ret) {
- DRM_ERROR("modeset init failed\n");
- goto err_scanouts;
+ if (vgdev->num_scanouts) {
+ ret = virtio_gpu_modeset_init(vgdev);
+ if (ret) {
+ DRM_ERROR("modeset init failed\n");
+ goto err_scanouts;
+ }
}
virtio_device_ready(vgdev->vdev);
@@ -246,10 +251,12 @@ 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
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