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Wed, 11 Dec 2019 21:13:33 -0800 Received: from MTKMBS07N2.mediatek.inc (172.21.101.141) by MTKMBS62DR.mediatek.inc (172.29.94.18) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 11 Dec 2019 21:13:47 -0800 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs07n2.mediatek.inc (172.21.101.141) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 12 Dec 2019 13:13:14 +0800 Received: from [172.21.77.33] (172.21.77.33) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Thu, 12 Dec 2019 13:12:53 +0800 Message-ID: <1576127609.27185.8.camel@mtkswgap22> Subject: Re: [PATCH v5 3/3] hwrng: add mtk-sec-rng driver From: Neal Liu To: Marc Zyngier Date: Thu, 12 Dec 2019 13:13:29 +0800 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> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191211_211336_432109_FA54DA10 X-CRM114-Status: GOOD ( 23.24 ) X-BeenThere: linux-mediatek@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@arm.com, Ard Biesheuvel , Catalin Marinas , Sean Wang , Linux Kernel Mailing List , wsd_upstream , Rob Herring , linux-mediatek@lists.infradead.org, linux-crypto@vger.kernel.org, Matt Mackall , Matthias Brugger , Crystal Guo =?UTF-8?Q?=28=E9=83=AD=E6=99=B6=29?= , Will Deacon , Lars Persson , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org 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. Thanks -Neal _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek