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Date:   Mon, 1 Jul 2019 18:02:38 +0100
From:   Will Deacon <will@kernel.org>
To:     "Saidi, Ali" <alisaidi@amazon.com>
Cc:     Will Deacon <will.deacon@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        "linux-arm-kernel@lists.infradead.org" 
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        Herbert Xu <herbert@gondor.apana.org.au>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Matt Mackall <mpm@selenic.com>,
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        "Rindjunsky, Ron" <ronrindj@amazon.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        "Woodhouse, David" <dwmw@amazon.co.uk>, marc.zyngier@arm.com
Subject: Re: [PATCH 0/3] Add support for Graviton TRNG
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[+Marc]

On Mon, Jul 01, 2019 at 09:28:06AM +0100, Will Deacon wrote:
> [Note: this was in my spam folder]
> 
> On Fri, Jun 28, 2019 at 06:05:10PM +0000, Saidi, Ali wrote:
> > On 6/7/19, 7:59 AM, " Ali Saidi" <alisaidi@amazon.com> wrote:
> >     On 6/5/19, 7:20 AM, "Will Deacon" <will.deacon@arm.com> wrote:
> >         On Tue, Jun 04, 2019 at 08:30:57PM +0000, Ali Saidi wrote:
> >         > AWS Graviton based systems provide an Arm SMC call in the vendor defined
> >         > hypervisor region to read random numbers from a HW TRNG and return them to the
> >         > guest. 
> >         > 
> >         > We've observed slower guest boot and especially reboot times due to lack of
> >         > entropy and providing access to a TRNG is meant to address this. 
> >         
> >         Curious, but why this over something like virtio-rng?
> >         
> >     This interface allows us to provide the functionality from both EL2
> >     and EL3 and support multiple different types of our instances which we
> >     unfortunately can't do with virt-io.
> >     
> > Any additional comments?
> > Do you know when you'll have a chance to rebase arm64/smccc-cleanup?
> 
> Sorry, Ali, this slipped through the cracks. Marc and I will chat today and
> look at respinning what we had before; it should then hopefully be
> straightforward enough for you to take that as a base for what you want to
> do.

Ok, I hacked on this a bit today and hopefully you can use this as a
starting point:

https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=kvm/hvc

I haven't given it any real testing, so apologies for the bugs.

Will