From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CDC1EC04A6B for ; Fri, 10 May 2019 12:38:52 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8E8EC20989 for ; Fri, 10 May 2019 12:38:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E8EC20989 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:42669 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hP4nb-0005i0-ST for qemu-devel@archiver.kernel.org; Fri, 10 May 2019 08:38:51 -0400 Received: from eggs.gnu.org ([209.51.188.92]:48417) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hP4mh-0005QV-VM for qemu-devel@nongnu.org; Fri, 10 May 2019 08:37:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hP4mg-0007HR-Jr for qemu-devel@nongnu.org; Fri, 10 May 2019 08:37:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51472) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hP4mg-0007HG-CG for qemu-devel@nongnu.org; Fri, 10 May 2019 08:37:54 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6122B3079B77; Fri, 10 May 2019 12:37:53 +0000 (UTC) Received: from [10.40.205.9] (unknown [10.40.205.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id B2A145D717; Fri, 10 May 2019 12:37:42 +0000 (UTC) To: Markus Armbruster References: <20190510102637.10209-1-lvivier@redhat.com> <87zhnuqyu0.fsf@dusky.pond.sub.org> From: Laurent Vivier Message-ID: <87991c2b-da9d-0e7f-bc09-9fbadbda4ef8@redhat.com> Date: Fri, 10 May 2019 14:37:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <87zhnuqyu0.fsf@dusky.pond.sub.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Fri, 10 May 2019 12:37:53 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v2] rng-builtin: add an RNG backend that uses qemu_guest_getrandom() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "=?UTF-8?Q?Daniel_P.Berrang=c3=a9?=" , Amit Shah , Kashyap Chamarthy , Richard Henderson , "Richard W . M . Jones" , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/05/2019 14:27, Markus Armbruster wrote: > Laurent Vivier 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 >> Signed-off-by: Laurent Vivier >> --- >> >> 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.henderson@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! > >> 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... Thanks, Laurent