From: Marc Zyngier <maz@kernel.org>
To: Neal Liu <neal.liu@mediatek.com>
Cc: "Florian Fainelli" <f.fainelli@gmail.com>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
pawel.moll@arm.com, "Mark Rutland" <mark.rutland@arm.com>,
DTML <devicetree@vger.kernel.org>,
"Herbert Xu" <herbert@gondor.apana.org.au>,
wsd_upstream <wsd_upstream@mediatek.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Sean Wang" <sean.wang@kernel.org>,
linux-mediatek@lists.infradead.org,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Rob Herring" <robh+dt@kernel.org>,
linux-crypto@vger.kernel.org, "Matt Mackall" <mpm@selenic.com>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"Crystal Guo (郭晶)" <crystal.guo@mediatek.com>,
"Will Deacon" <will@kernel.org>, "Lars Persson" <lists@bofh.nu>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 3/3] hwrng: add mtk-sec-rng driver
Date: Thu, 12 Dec 2019 11:45:56 +0000 [thread overview]
Message-ID: <a5982b8ed10440eef14c04df6e6060b6@www.loen.fr> (raw)
In-Reply-To: <1576127609.27185.8.camel@mtkswgap22>
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...
next prev parent reply other threads:[~2019-12-12 11:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 14:22 [PATCH v5 0/3] MediaTek Security random number generator support Neal Liu
2019-11-27 14:22 ` [PATCH v5 1/3] soc: mediatek: add SMC fid table for SIP interface Neal Liu
2019-11-27 14:22 ` [PATCH v5 2/3] dt-bindings: rng: add bindings for MediaTek ARMv8 SoCs Neal Liu
2019-11-27 14:22 ` [PATCH v5 3/3] hwrng: add mtk-sec-rng driver Neal Liu
2019-11-27 15:03 ` Ard Biesheuvel
2019-11-28 15:02 ` Neal Liu
2019-11-29 10:02 ` Lars Persson
2019-11-29 11:30 ` Neal Liu
2019-12-02 16:12 ` Ard Biesheuvel
2019-12-02 19:11 ` Marc Zyngier
2019-12-03 4:16 ` Florian Fainelli
2019-12-03 11:17 ` Marc Zyngier
2019-12-12 5:13 ` Neal Liu
2019-12-12 11:45 ` Marc Zyngier [this message]
2019-12-12 14:03 ` Ard Biesheuvel
2019-12-12 14:30 ` Marc Zyngier
2019-12-03 10:17 ` Will Deacon
2019-12-12 14:43 ` Sudeep Holla
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a5982b8ed10440eef14c04df6e6060b6@www.loen.fr \
--to=maz@kernel.org \
--cc=ard.biesheuvel@linaro.org \
--cc=catalin.marinas@arm.com \
--cc=crystal.guo@mediatek.com \
--cc=devicetree@vger.kernel.org \
--cc=f.fainelli@gmail.com \
--cc=herbert@gondor.apana.org.au \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=lists@bofh.nu \
--cc=mark.rutland@arm.com \
--cc=matthias.bgg@gmail.com \
--cc=mpm@selenic.com \
--cc=neal.liu@mediatek.com \
--cc=pawel.moll@arm.com \
--cc=robh+dt@kernel.org \
--cc=sean.wang@kernel.org \
--cc=will@kernel.org \
--cc=wsd_upstream@mediatek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).