On 12/2/2019 11:11 AM, Marc Zyngier wrote: > On Mon, 2 Dec 2019 16:12:09 +0000 > Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > >> (adding some more arm64 folks) >> >> On Fri, 29 Nov 2019 at 11:30, Neal Liu <neal.liu@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> 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. -- Florian
