On 08/04/2019 08:31, Herbert Xu wrote: > On Fri, Mar 29, 2019 at 05:30:11PM +0100, Laurent Vivier wrote: >> If the device is not ready to provide data the kernel will >> be stuck indefinitely in the init function. >> >> This is not a problem if the device is driven using a module, >> but if the driver is linked directly into the kernel then the >> kernel boot sequence hangs. >> >> This can happen with virtio-rng device with rng-egd backend >> with no data provider, for instance with QEMU command line parameters: >> >> ... >> -chardev socket,id=charrng0,host=localhost,port=2345,server,nowait \ >> -object rng-egd,id=objrng0,chardev=charrng0 \ >> -device virtio-rng-pci,rng=objrng0,id=rng0 >> >> To avoid that, we can call rng_get_data() in non blocking mode because >> the function already manages the case where byte_read is >> 0 (if the device is not already initialized). >> >> See also commit d3cc7996473a >> ("hwrng: fetch randomness only after device init") >> >> Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx> > > I think this is either not a bug (make sure that the user supplies > a RNG source) or it should be addressed in virtio-rng. Yes, I did more investigation and I agree. Thanks, Laurent