From: Igor Torrente Date: Thu, 7 Aug 2025 12:41:45 +0000 (-0300) Subject: Revert "virtio: reject shm region if length is zero" X-Git-Tag: v6.17-rc4~24^2~3 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=ced17ee32a9988b8a260628e7c31a100d7dc082e;p=users%2Fgriffoul%2Flinux.git Revert "virtio: reject shm region if length is zero" 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 Message-Id: <20250807124145.81816-1-igor.torrente@collabora.com> Signed-off-by: Michael S. Tsirkin --- diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h index 918cf25cd3c69..8bf156dde554a 100644 --- a/include/linux/virtio_config.h +++ b/include/linux/virtio_config.h @@ -328,8 +328,6 @@ 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);