Messages in this thread | | | Subject | Re: [PATCH v5 3/3] hwrng: add mtk-sec-rng driver | Date | Thu, 12 Dec 2019 11:45:56 +0000 | From | Marc Zyngier <> |
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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 <ard.biesheuvel@linaro.org> wrote: >> >> >> >>> (adding some more arm64 folks) >> >>> >> >>> On Fri, 29 Nov 2019 at 11:30, Neal Liu <neal.liu@mediatek.com> >> >>> 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 >> <neal.liu@mediatek.com> >> >>>>> 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.
Thanks,
M. -- Jazz is not dead. It just smells funny...
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