From: Laurent Vivier <laur...@vivier.eu>
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>
Message-Id: <20201220163539.2255963-1-laur...@vivier.eu>
Acked-by: Gerd Hoffmann <kra...@redhat.com>
Reviewed-by: Stefano Garzarella <sgarz...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
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 e1b5c3b81e..610661d6a5 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:
--
MST
