On Sun, Dec 20, 2020 at 05:35:39PM +0100, Laurent Vivier wrote:
In the kernel, virtio_gpu_init() uses virtio_get_shm_region() since commit 6076a9711dc5 ("drm/virtio: implement blob resources: probe for host visible region") but vm_get_shm_region() unconditionally uses VIRTIO_MMIO_SHM_SEL to get the address and the length of the region.commit 38e895487afc ("virtio: Implement get_shm_region for MMIO transport" As this is not implemented in QEMU, address and length are 0 and passed as is to devm_request_mem_region() that triggers a crash: [drm:virtio_gpu_init] *ERROR* Could not reserve host visible region Unable to handle kernel NULL pointer dereference at virtual address (ptrval) According to the comments in the kernel, a non existent shared region has a length of (u64)-1. This is what we return now with this patch to disable the region. Signed-off-by: Laurent Vivier <laur...@vivier.eu> --- hw/virtio/virtio-mmio.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c index e1b5c3b81e37..610661d6a526 100644 --- a/hw/virtio/virtio-mmio.c +++ b/hw/virtio/virtio-mmio.c @@ -191,6 +191,14 @@ static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size) return 0; } return vdev->generation; + case VIRTIO_MMIO_SHM_LEN_LOW: + case VIRTIO_MMIO_SHM_LEN_HIGH: + /* + * VIRTIO_MMIO_SHM_SEL is unimplemented + * according to the linux driver, if region length is -1 + * the shared memory doesn't exist + */ + return -1; case VIRTIO_MMIO_DEVICE_FEATURES_SEL: case VIRTIO_MMIO_DRIVER_FEATURES: case VIRTIO_MMIO_DRIVER_FEATURES_SEL: -- 2.29.2
Reviewed-by: Stefano Garzarella <sgarz...@redhat.com>
