6.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Igor Torrente igor.torrente@collabora.com
[ Upstream commit ced17ee32a9988b8a260628e7c31a100d7dc082e ]
The commit 206cc44588f7 ("virtio: reject shm region if length is zero") breaks the Virtio-gpu `host_visible` feature.
As you can see in the snippet below, host_visible_region is zero because of the `kzalloc`. It's using the `vm_get_shm_region` (drivers/virtio/virtio_mmio.c:536) to read the `addr` and `len` from qemu/crosvm.
``` drivers/gpu/drm/virtio/virtgpu_kms.c 132 vgdev = drmm_kzalloc(dev, sizeof(struct virtio_gpu_device), GFP_KERNEL); [...] 177 if (virtio_get_shm_region(vgdev->vdev, &vgdev->host_visible_region, 178 VIRTIO_GPU_SHM_ID_HOST_VISIBLE)) { ``` Now it always fails.
To fix, revert the offending commit.
Fixes: 206cc44588f7 ("virtio: reject shm region if length is zero") Signed-off-by: Igor Torrente igor.torrente@collabora.com Message-Id: 20250807124145.81816-1-igor.torrente@collabora.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/virtio_config.h | 2 -- 1 file changed, 2 deletions(-)
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h index b3e1d30c765bc..169c7d367facb 100644 --- a/include/linux/virtio_config.h +++ b/include/linux/virtio_config.h @@ -329,8 +329,6 @@ static inline bool virtio_get_shm_region(struct virtio_device *vdev, struct virtio_shm_region *region, u8 id) { - if (!region->len) - return false; if (!vdev->config->get_shm_region) return false; return vdev->config->get_shm_region(vdev, region, id);