On (Fri) 10 May 2019 [17:19:12], Markus Armbruster wrote: > Laurent Vivier <lviv...@redhat.com> writes: > > > On 10/05/2019 14:27, Markus Armbruster wrote: > >> Laurent Vivier <lviv...@redhat.com> writes: > >> > >>> Add a new RNG backend using QEMU builtin getrandom function. > >>> > >>> It can be created and used with something like: > >>> > >>> ... -object rng-builtin,id=rng0 -device virtio-rng,rng=rng0 ... > >>> > >>> Reviewed-by: Richard Henderson <richard.hender...@linaro.org> > >>> Signed-off-by: Laurent Vivier <lviv...@redhat.com> > >>> --- > >>> > >>> Notes: > >>> This patch applies on top of > >>> "[PATCH v5 00/24] Add qemu_getrandom and ARMv8.5-RNG etc" > >>> Based-on: 20190510012458.22706-1-richard.hender...@linaro.org > >>> v2: Update qemu-options.hx > >>> describe the new backend and specify virtio-rng uses the > >>> rng-random by default (do we want to change this?) > >>> > >>> backends/Makefile.objs | 2 +- > >>> backends/rng-builtin.c | 56 ++++++++++++++++++++++++++++++++++++++++++ > >>> qemu-options.hx | 10 +++++++- > >>> 3 files changed, 66 insertions(+), 2 deletions(-) > >>> create mode 100644 backends/rng-builtin.c > >>> > >>> diff --git a/backends/Makefile.objs b/backends/Makefile.objs > >>> index ff619d31b461..8da4a508d97b 100644 > >>> --- a/backends/Makefile.objs > >>> +++ b/backends/Makefile.objs > >>> @@ -1,4 +1,4 @@ > >>> -common-obj-y += rng.o rng-egd.o > >>> +common-obj-y += rng.o rng-egd.o rng-builtin.o > >>> common-obj-$(CONFIG_POSIX) += rng-random.o > >>> common-obj-$(CONFIG_TPM) += tpm.o > >>> diff --git a/backends/rng-builtin.c b/backends/rng-builtin.c > >>> new file mode 100644 > >>> index 000000000000..b1264b745407 > >>> --- /dev/null > >>> +++ b/backends/rng-builtin.c > >>> @@ -0,0 +1,56 @@ > >>> +/* > >>> + * QEMU Builtin Random Number Generator Backend > >>> + * > >>> + * This work is licensed under the terms of the GNU GPL, version 2 or > >>> later. > >>> + * See the COPYING file in the top-level directory. > >>> + */ > >>> + > >>> +#include "qemu/osdep.h" > >>> +#include "sysemu/rng.h" > >>> +#include "qapi/error.h" > >>> +#include "qapi/qmp/qerror.h" > >>> +#include "qemu/main-loop.h" > >>> +#include "qemu/guest-random.h" > >>> + > >>> +#define TYPE_RNG_BUILTIN "rng-builtin" > >>> +#define RNG_BUILTIN(obj) OBJECT_CHECK(RngBuiltin, (obj), > >>> TYPE_RNG_BUILTIN) > >>> + > >>> +typedef struct RngBuiltin { > >>> + RngBackend parent; > >>> +} RngBuiltin; > >>> + > >>> +static void rng_builtin_request_entropy(RngBackend *b, RngRequest *req) > >>> +{ > >>> + RngBuiltin *s = RNG_BUILTIN(b); > >>> + > >>> + while (!QSIMPLEQ_EMPTY(&s->parent.requests)) { > >>> + RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests); > >>> + > >>> + qemu_guest_getrandom_nofail(req->data, req->size); > >>> + > >>> + req->receive_entropy(req->opaque, req->data, req->size); > >>> + > >>> + rng_backend_finalize_request(&s->parent, req); > >>> + } > >>> +} > >>> + > >>> +static void rng_builtin_class_init(ObjectClass *klass, void *data) > >>> +{ > >>> + RngBackendClass *rbc = RNG_BACKEND_CLASS(klass); > >>> + > >>> + rbc->request_entropy = rng_builtin_request_entropy; > >>> +} > >>> + > >>> +static const TypeInfo rng_builtin_info = { > >>> + .name = TYPE_RNG_BUILTIN, > >>> + .parent = TYPE_RNG_BACKEND, > >>> + .instance_size = sizeof(RngBuiltin), > >>> + .class_init = rng_builtin_class_init, > >>> +}; > >>> + > >>> +static void register_types(void) > >>> +{ > >>> + type_register_static(&rng_builtin_info); > >>> +} > >>> + > >>> +type_init(register_types); > >>> diff --git a/qemu-options.hx b/qemu-options.hx > >>> index 0191ef8b1eb7..3e2a51c691b0 100644 > >>> --- a/qemu-options.hx > >>> +++ b/qemu-options.hx > >>> @@ -4280,13 +4280,21 @@ other options. > >>> The @option{share} boolean option is @var{on} by default with > >>> memfd. > >>> +@item -object rng-builtin,id=@var{id} > >>> + > >>> +Creates a random number generator backend which obtains entropy from > >>> +QEMU builtin functions. The @option{id} parameter is a unique ID that > >>> +will be used to reference this entropy backend from the > >>> @option{virtio-rng} > >>> +device. > >>> + > >>> @item -object rng-random,id=@var{id},filename=@var{/dev/random} > >>> Creates a random number generator backend which obtains entropy > >>> from > >>> a device on the host. The @option{id} parameter is a unique ID that > >>> will be used to reference this entropy backend from the > >>> @option{virtio-rng} > >>> device. > >> > >> There's also the "spapr-rng" device, I think. > > > > spapr-rng doesn't have default. You must specify one to be able to use it: > > qemu-system-ppc64: -device spapr-rng: spapr-rng needs an RNG backend! > > You're right. > > >>> The @option{filename} parameter specifies which file to obtain > >>> -entropy from and if omitted defaults to @option{/dev/random}. > >>> +entropy from and if omitted defaults to @option{/dev/random}. By default, > >>> +the @option{virtio-rng} device uses this RNG backend. > >>> @item -object rng-egd,id=@var{id},chardev=@var{chardevid} > >> > >> Trivial conflict with Kashyap's "[PATCH v2] VirtIO-RNG: Update default > >> entropy source to `/dev/urandom`". > >> > >> virtio-rng indeed creates an rng-random backend when the user doesn't > >> specify one. I consider having device model frontends create backends a > >> bad idea. Not this patch's fault, of course. > >> > >> That said, would rng-builtin be a better default? For starters, it's > >> available when !CONFIG_POSIX. I suspect virtio-rng crashes when it > >> tries to create an rng-random that isn't available. > > > > I will send a v3 with rng-builtin as a default. Maintainer will be > > able to pick one of his choice, v2 or v3. > > > >> > >> The new rng-builtin is considerably simpler than both rng-random and > >> rng-egd. Moreover, it just works, whereas rng-random is limited to > >> CONFIG_POSIX, and rng-egd needs egd running (which I suspect basically > >> nobody does). Have we considered deprecating these two backends in > >> favor of rng-builtin? > > > > I have several bugzilla involving these backends: as there are > > blocking, the virtio-rng device in the guest can hang, or crash during > > hot-unplug. From my point of view, life would be easier without > > them... > > Sounds like perfectly fine reasons for deprecating them. Amit, what do > you think?
The egd backend wasn't too useful - so I don't mind deprecating it using the usual deprecation notice. The rng-random backend can stay with the multiple fallbacks as discussed in the other threads - with getrandom() being the most preferred one on Linux. BSDs have /dev/srandom which is quite similar to getrandom(), but that can be an additional backend that can come later. Overall, I like the way these series turned out.. Amit -- http://amitshah.net/