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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 97E76C2D0C9 for ; Thu, 12 Dec 2019 14:30:54 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6CAE02067C for ; Thu, 12 Dec 2019 14:30:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Dri66QXo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CAE02067C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:From:Date: MIME-Version:Subject:To:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Nx1cPE/PODVZs+P2HWp0VecGGKbXvwwVp0wOMoWjhKw=; b=Dri66QXo3HxQGDWryPpzNyFO1 KQLRFZFu/grg7H+LAZId4g49O3ABptz0PMXwgQ+HYhxfHmmO1YQpgswyNFPtHihSn1l7NoixzSa4+ Z3DllkfT0uZs/YyC9au4mxqqGE8NyNIpgH4Xs4cp7WJfJw4Eim9gT9+yApvd9tiaT7PImBxkGllcs wUz41f2xyh5Kw02dhL1aNUtHFki1uU+WRRA7p0vMdl2VBPVe3m6ExSwO9E5fQmFVLDws48xuq0Bsj s3QR6IDyMUD3DRuRikqiXvdL9YRPTmuZFHBS1V0hpePW8aO5CVa/cJPdqz6wtJ2G0JOh2ogpAvGH5 VAbnkjCzA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ifPUT-0003YW-TB; Thu, 12 Dec 2019 14:30:53 +0000 Received: from inca-roads.misterjones.org ([213.251.177.50]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ifPUP-0003Xe-6O; Thu, 12 Dec 2019 14:30:50 +0000 Received: from www-data by cheepnis.misterjones.org with local (Exim 4.80) (envelope-from ) id 1ifPUF-0002s6-2y; Thu, 12 Dec 2019 15:30:39 +0100 To: Ard Biesheuvel Subject: Re: [PATCH v5 3/3] hwrng: add mtk-sec-rng driver X-PHP-Originating-Script: 0:main.inc MIME-Version: 1.0 Date: Thu, 12 Dec 2019 14:30:38 +0000 From: Marc Zyngier In-Reply-To: References: <1574864578-467-1-git-send-email-neal.liu@mediatek.com> <1574864578-467-4-git-send-email-neal.liu@mediatek.com> <1575027046.24848.4.camel@mtkswgap22> <20191202191146.79e6368c@why> <299029b0-0689-c2c4-4656-36ced31ed513@gmail.com> <1576127609.27185.8.camel@mtkswgap22> Message-ID: <9de12c45b4b022cfb01d89ca56429d53@www.loen.fr> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/0.7.2 X-SA-Exim-Connect-IP: X-SA-Exim-Rcpt-To: ard.biesheuvel@linaro.org, neal.liu@mediatek.com, f.fainelli@gmail.com, pawel.moll@arm.com, mark.rutland@arm.com, devicetree@vger.kernel.org, herbert@gondor.apana.org.au, wsd_upstream@mediatek.com, catalin.marinas@arm.com, sean.wang@kernel.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-crypto@vger.kernel.org, mpm@selenic.com, matthias.bgg@gmail.com, crystal.guo@mediatek.com, will@kernel.org, lists@bofh.nu, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191212_063049_378599_54C2F1E5 X-CRM114-Status: GOOD ( 23.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , DTML , Florian Fainelli , Herbert Xu , Pawel Moll , Catalin Marinas , Sean Wang , Linux Kernel Mailing List , wsd_upstream , =?UTF-8?Q?Crystal_Guo_=28=E9=83=AD=E6=99=B6=29?= , Rob Herring , Neal Liu , "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , Matt Mackall , Matthias Brugger , "moderated list:ARM/Mediatek SoC support" , Will Deacon , Lars Persson , linux-arm-kernel Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2019-12-12 14:03, Ard Biesheuvel wrote: > On Thu, 12 Dec 2019 at 12:45, Marc Zyngier wrote: >> >> On 2019-12-12 05:13, Neal Liu wrote: >> > On Tue, 2019-12-03 at 11:17 +0000, Marc Zyngier wrote: >> >> On 2019-12-03 04:16, Florian Fainelli wrote: >> >> > On 12/2/2019 11:11 AM, Marc Zyngier wrote: >> >> >> On Mon, 2 Dec 2019 16:12:09 +0000 >> >> >> Ard Biesheuvel wrote: >> >> >> >> >> >>> (adding some more arm64 folks) >> >> >>> >> >> >>> On Fri, 29 Nov 2019 at 11:30, Neal Liu >> >> >> >>> wrote: >> >> >>>> >> >> >>>> On Fri, 2019-11-29 at 18:02 +0800, Lars Persson wrote: >> >> >>>>> Hi Neal, >> >> >>>>> >> >> >>>>> On Wed, Nov 27, 2019 at 3:23 PM Neal Liu >> >> >> >> >>>>> wrote: >> >> >>>>>> >> >> >>>>>> For MediaTek SoCs on ARMv8 with TrustZone enabled, >> >> peripherals >> >> >>>>>> like >> >> >>>>>> entropy sources is not accessible from normal world >> (linux) >> >> and >> >> >>>>>> rather accessible from secure world (ATF/TEE) only. This >> >> driver >> >> >>>>>> aims >> >> >>>>>> to provide a generic interface to ATF rng service. >> >> >>>>>> >> >> >>>>> >> >> >>>>> I am working on several SoCs that also will need this kind >> of >> >> >>>>> driver >> >> >>>>> to get entropy from Arm trusted firmware. >> >> >>>>> If you intend to make this a generic interface, please >> clean >> >> up >> >> >>>>> the >> >> >>>>> references to MediaTek and give it a more generic name. For >> >> >>>>> example >> >> >>>>> "Arm Trusted Firmware random number driver". >> >> >>>>> >> >> >>>>> It will also be helpful if the SMC call number is >> >> configurable. >> >> >>>>> >> >> >>>>> - Lars >> >> >>>> >> >> >>>> Yes, I'm trying to make this to a generic interface. I'll >> try >> >> to >> >> >>>> make >> >> >>>> HW/platform related dependency to be configurable and let it >> >> more >> >> >>>> generic. >> >> >>>> Thanks for your suggestion. >> >> >>>> >> >> >>> >> >> >>> I don't think it makes sense for each arm64 platform to >> expose >> >> an >> >> >>> entropy source via SMC calls in a slightly different way, and >> >> model >> >> >>> it >> >> >>> as a h/w driver. Instead, we should try to standardize this, >> and >> >> >>> perhaps expose it via the architectural helpers that already >> >> exist >> >> >>> (get_random_seed_long() and friends), so they get plugged >> into >> >> the >> >> >>> kernel random pool driver directly. >> >> >> >> >> >> Absolutely. I'd love to see a standard, ARM-specified, >> >> virtualizable >> >> >> RNG that is abstracted from the HW. >> >> > >> >> > Do you think we could use virtio-rng on top of a modified >> >> virtio-mmio >> >> > which instead of being backed by a hardware mailbox, could use >> >> > hvc/smc >> >> > calls to signal writes to shared memory and get notifications >> via >> >> an >> >> > interrupt? This would also open up the doors to other virtio >> uses >> >> > cases >> >> > beyond just RNG (e.g.: console, block devices?). If this is >> >> > completely >> >> > stupid, then please disregard this comment. >> >> >> >> The problem with a virtio device is that it is a ... device. What >> we >> >> want >> >> is to be able to have access to an entropy source extremely early >> in >> >> the >> >> kernel life, and devices tend to be available pretty late in the >> >> game. >> >> This means we cannot plug them in the architectural helpers that >> Ard >> >> mentions above. >> >> >> >> What you're suggesting looks more like a new kind of virtio >> >> transport, >> >> which is interesting, in a remarkably twisted way... ;-) >> >> >> >> Thanks, >> >> >> >> M. >> > >> > In conclusion, is it helpful that hw_random has a generic >> interface >> > to >> > add device randomness by talking to hwrng which is implemented in >> the >> > firmware or the hypervisor? >> > For most chip vendors, I think the answer is yes. We already >> prepared >> > a >> > new patchset and need you agree with this idea. >> >> As long as it is a *unified* interface, I'm all for that. >> > > > Yeah, but I'm not sure it makes sense to model it as a device like > this. It would be nice if we could tie this into the ARM SMCCC > discovery, and use the SMC calls to back arch_get_random_seed_long() Probably I wasn't clear enough, but that's really what I meant by a unified interface (implemented by the firmware or the hypervisor). > [provided we fix the braindead way in which that is being used today > in the interrupt code] Ah, I said I'd look into it. Thanks for the reminder... Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel