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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 57AA7C28CC5 for ; Wed, 5 Jun 2019 18:38:38 +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 33DB8206B8 for ; Wed, 5 Jun 2019 18:38:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 33DB8206B8 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]:48259 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hYao1-0003TB-7p for qemu-devel@archiver.kernel.org; Wed, 05 Jun 2019 14:38:37 -0400 Received: from eggs.gnu.org ([209.51.188.92]:45637) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hYamV-0002dr-2K for qemu-devel@nongnu.org; Wed, 05 Jun 2019 14:37:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hYamT-0008Qr-CF for qemu-devel@nongnu.org; Wed, 05 Jun 2019 14:37:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39408) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hYamT-0008Pd-6D for qemu-devel@nongnu.org; Wed, 05 Jun 2019 14:37:01 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 84C923092669; Wed, 5 Jun 2019 18:36:59 +0000 (UTC) Received: from [10.40.204.44] (ovpn-204-44.brq.redhat.com [10.40.204.44]) by smtp.corp.redhat.com (Postfix) with ESMTP id 19EFB1001DD1; Wed, 5 Jun 2019 18:36:52 +0000 (UTC) To: Markus Armbruster References: <20190529143106.11789-1-lvivier@redhat.com> <87a7ewp4h4.fsf@dusky.pond.sub.org> <4601cfa8-732a-3063-7106-da8d3b990410@redhat.com> <87v9xjlxuu.fsf@dusky.pond.sub.org> From: Laurent Vivier Message-ID: Date: Wed, 5 Jun 2019 20:36:46 +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: <87v9xjlxuu.fsf@dusky.pond.sub.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Wed, 05 Jun 2019 18:36:59 +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 v7 0/4] 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?=" , Kashyap Chamarthy , Amit Shah , Richard Henderson , qemu-devel@nongnu.org, "Richard W . M . Jones" , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 05/06/2019 19:56, Markus Armbruster wrote: > Laurent Vivier writes: > >> On 05/06/2019 15:05, Markus Armbruster wrote: >>> Laurent Vivier writes: >>> >>>> Add a new RNG backend using QEMU builtin getrandom function. >>>> >>>> v7: rebase on master >>>> Make rng-builtin asynchronous with QEMUBH (removed existing R-b) >>> >>> Pardon the ignorant question: why is that necessary? >>> >> >> Because request_entropy() function is called while the request is not in >> the requests queue, so the loop on !QSIMPLEQ_EMPTY(&s->parent.requests) >> doens't process it. The request is added just after the call. > > In rng_backend_request_entropy(). I see. Any particular reason for > this order? "I don't know" is an acceptable answer :) > Yes... and there is a reason: in rng_random_request_entropy(), QSIMPLEQ_EMPTY() is used to know if we have to register an fd handler with qemu_set_fd_handler(). For me, it seemed easier to use QEMUBH rather than to change the existing algorithm, as the backend has been thought to be asynchronous. Thanks, Laurent