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 <[email protected]> wrote:
> >>
> >>> (adding some more arm64 folks)
> >>>
> >>> On Fri, 29 Nov 2019 at 11:30, Neal Liu <[email protected]>
> >>> 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 <[email protected]>
> >>>>> 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
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 <[email protected]> wrote:
>> >>
>> >>> (adding some more arm64 folks)
>> >>>
>> >>> On Fri, 29 Nov 2019 at 11:30, Neal Liu <[email protected]>
>> >>> 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
>> <[email protected]>
>> >>>>> 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...
On Thu, 12 Dec 2019 at 12:45, Marc Zyngier <[email protected]> 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 <[email protected]> wrote:
> >> >>
> >> >>> (adding some more arm64 folks)
> >> >>>
> >> >>> On Fri, 29 Nov 2019 at 11:30, Neal Liu <[email protected]>
> >> >>> 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
> >> <[email protected]>
> >> >>>>> 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()
[provided we fix the braindead way in which that is being used today
in the interrupt code]
On 2019-12-12 14:03, Ard Biesheuvel wrote:
> On Thu, 12 Dec 2019 at 12:45, Marc Zyngier <[email protected]> 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 <[email protected]> wrote:
>> >> >>
>> >> >>> (adding some more arm64 folks)
>> >> >>>
>> >> >>> On Fri, 29 Nov 2019 at 11:30, Neal Liu
>> <[email protected]>
>> >> >>> 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
>> >> <[email protected]>
>> >> >>>>> 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...