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[209.51.188.17]) by mx.google.com with ESMTPS id t22si8941661itc.99.2019.03.26.11.42.50 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 26 Mar 2019 11:42:50 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; spf=pass (google.com: domain of qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([127.0.0.1]:36406 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h8r29-0008CG-Hd for alex.bennee@linaro.org; Tue, 26 Mar 2019 14:42:49 -0400 Received: from eggs.gnu.org ([209.51.188.92]:58672) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h8r06-0007Ba-R4 for qemu-devel@nongnu.org; Tue, 26 Mar 2019 14:40:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h8qvw-0000Mf-Vv for qemu-devel@nongnu.org; Tue, 26 Mar 2019 14:36:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59566) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1h8qvv-0000LL-1e; Tue, 26 Mar 2019 14:36:23 -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 947EA811AC; Tue, 26 Mar 2019 18:36:21 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-116.ams2.redhat.com [10.36.116.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2DD0C17595; Tue, 26 Mar 2019 18:36:21 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 81E591138648; Tue, 26 Mar 2019 19:36:19 +0100 (CET) From: Markus Armbruster To: Laszlo Ersek References: <20190325125142.11628-1-zhengxiang9@huawei.com> <19929558-9f2d-148a-4357-d48b46f8b62b@huawei.com> <87va06kvm6.fsf@dusky.pond.sub.org> <59f100b4-f6e9-973d-532b-58fb172a7009@redhat.com> <87imw5fv45.fsf@dusky.pond.sub.org> Date: Tue, 26 Mar 2019 19:36:19 +0100 In-Reply-To: (Laszlo Ersek's message of "Tue, 26 Mar 2019 18:10:36 +0100") Message-ID: <8736n9eb4s.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain 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 [10.5.110.27]); Tue, 26 Mar 2019 18:36:21 +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] [RFC PATCH] hw/arm/virt: use variable size of flash device to save memory 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: Peter Maydell , Ard Biesheuvel , QEMU Developers , Zheng Xiang , qemu-arm , Heyi Guo , wanghaibin.wang@huawei.com Errors-To: qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-devel" X-TUID: W7re17mzCW4r Laszlo Ersek writes: > On 03/26/19 17:39, Markus Armbruster wrote: >> Laszlo Ersek writes: > >>> With the dynamic sizing in QEMU (which, IIRC, I had originally >>> introduced still in the 1MB times, due to the split between the >>> executable and varstore parts), both the 1MB->2MB switch, and the >>> 2MB->4MB switch in the firmware caused zero pain in QEMU. And right now, >>> 4MB looks like a "sweet spot", with some elbow room left. >> >> Explicit configuration would've been exactly as painless. Even with >> pflash sizes restricted to powers of two. > > I wrote the patch that ended up as commit 637a5acb46b3 -- with your R-b > -- in 2013. I'm unsure if machine type properties existed back then, but > even if they did, do you think I knew about them? :) > > You are right, of course; it's just that we can't tell the future. True! All we can do is continue to design as well as we can given the information, experience and resources we have, and when the inevitable design mistakes become apparent, limit their impact. Some of the things we now consider mistakes we just didn't see. Others we saw (e.g. multiple pflash devices, unlike physical hardware), but underestimated their impact. [...]