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From: Sudeep Holla <sudeep.holla@arm.com>
To: Etienne CARRIERE <etienne.carriere@st.com>
Cc: Sumit Garg <sumit.garg@linaro.org>, Marc Zyngier <maz@kernel.org>,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	OP-TEE TrustedFirmware <op-tee@lists.trustedfirmware.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Jerome Forissier <jerome@forissier.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Ard Biesheuvel <ardb@kernel.org>,
	Etienne Carriere <etienne.carriere@linaro.org>
Subject: Re: [PATCH v2 0/7] Asynchronous notifications from secure world
Date: Tue, 13 Jul 2021 12:11:43 +0100	[thread overview]
Message-ID: <20210713111143.g6ztdakegs6ck25s@bogus> (raw)
In-Reply-To: <PAXPR10MB4687E737261282B78600272DFD189@PAXPR10MB4687.EURPRD10.PROD.OUTLOOK.COM>

On Fri, Jul 09, 2021 at 08:05:57AM +0000, Etienne CARRIERE wrote:
> Hello Sudeep and all,
> 
> On Wed, 7 Jul 2021 at 19:52, Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > Hi Sumit,
> >
> > I was holding off you reply as I didn't have all the background on this.
> > Achin did mention that this is preparatory work for FFA notifications.
> > I did mention to him that this is more than that, it is custom extension
> > to address what FF-A notification is trying to in standard way.
> >
> > I share same opinion as Marc Z.
> >
> > On Wed, Jul 07, 2021 at 11:22:23AM +0530, Sumit Garg wrote:
> > > On Tue, 6 Jul 2021 at 18:16, Marc Zyngier <maz@kernel.org> wrote:
> >
> > [...]
> >
> > > >
> > > > I don't care about OP-TEE. If you are proposing a contract between S
> > > > and NS, it has to be TEE and OS independent. That's how the
> > > > architecture works.
> > > >
> > >
> > > Agree, here we are not proposing a common contract among the S and NS
> > > world that every TEE (based on Arm TrustZone) will use to communicate
> > > with REE (Linux in our case) but rather an OP-TEE specific
> > > notifications feature that is built on top of OP-TEE specific ABIs.
> > >
> > > And I can see your arguments coming from an FFA perspective but there
> > > are platforms like the ones based on Armv7 which don't support FFA
> > > ABI. Maybe Jens can elaborate how this feature will fit in when FFA
> > > comes into picture?
> > >
> >
> > I can understand that but won't those platforms add the support both in
> > the kernel(current series) and secure world to address notifications.
> > While you could argue that it is small extension to what is already present
> > but I prefer they support FF-A is they need such a support instead of adding
> > custom mechanisms. It is hard to maintain and each vendor will deviate
> > from this custom mechanism and soon we will have bunch of them to handle.
>
> There exist armv7-a platforms that expect OP-TEE notification support and
> will not move the FF-A, like the stm32mp15. This platform won't move to FF-A
> mainly due to the memory cost of the added SPM layer and the device physical
> constraints.

Fair enough on the use-case and the analysis for not being able to use FF-A.
As you may already know it doesn't simply this problem. This has been
discussed for years and FF-A was assumed to be the solution when FF-A
spec work started.

> We have a usecase for OP-TEE notification. We're working on the integration
> of an SCMI server in OP-TEE. SCMI notification is a feature needed is this
> scope and it requires OP-TEE async notification means as those proposed
> here.
>

I am aware of this use-case, I understand. But I can only share rants
which I know doesn't help much.

> This OP-TEE async notif also brings a lot of value in OP-TEE as it allows a
> OP-TEE secure thread (i.e. executing a trusted application service) to
> gently wait on a secure interrupt (as a slow bus transaction completion or
> many other usecase) with the CPU relaxed. This support is provided by the
> proposed series. I believe existing device should be able to leverage this
> OP-TEE feature without needing their OP-TEE to move to the new FF-A
> interface.
>

While I agree these are nice to have in OPTEE, the timing is just odd.

We are trying hard to push FF-A as standard solution to address all such
issues that couldn't be solved with OPTEE + DT, now we are back to address
the same in parallel to FF-A.

--
Regards,
Sudeep

WARNING: multiple messages have this Message-ID
From: Sudeep Holla <sudeep.holla@arm.com>
To: Etienne CARRIERE <etienne.carriere@st.com>
Cc: Sumit Garg <sumit.garg@linaro.org>, Marc Zyngier <maz@kernel.org>,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	OP-TEE TrustedFirmware <op-tee@lists.trustedfirmware.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Jerome Forissier <jerome@forissier.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Ard Biesheuvel <ardb@kernel.org>,
	Etienne Carriere <etienne.carriere@linaro.org>
Subject: Re: [PATCH v2 0/7] Asynchronous notifications from secure world
Date: Tue, 13 Jul 2021 12:11:43 +0100	[thread overview]
Message-ID: <20210713111143.g6ztdakegs6ck25s@bogus> (raw)
In-Reply-To: <PAXPR10MB4687E737261282B78600272DFD189@PAXPR10MB4687.EURPRD10.PROD.OUTLOOK.COM>

On Fri, Jul 09, 2021 at 08:05:57AM +0000, Etienne CARRIERE wrote:
> Hello Sudeep and all,
> 
> On Wed, 7 Jul 2021 at 19:52, Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > Hi Sumit,
> >
> > I was holding off you reply as I didn't have all the background on this.
> > Achin did mention that this is preparatory work for FFA notifications.
> > I did mention to him that this is more than that, it is custom extension
> > to address what FF-A notification is trying to in standard way.
> >
> > I share same opinion as Marc Z.
> >
> > On Wed, Jul 07, 2021 at 11:22:23AM +0530, Sumit Garg wrote:
> > > On Tue, 6 Jul 2021 at 18:16, Marc Zyngier <maz@kernel.org> wrote:
> >
> > [...]
> >
> > > >
> > > > I don't care about OP-TEE. If you are proposing a contract between S
> > > > and NS, it has to be TEE and OS independent. That's how the
> > > > architecture works.
> > > >
> > >
> > > Agree, here we are not proposing a common contract among the S and NS
> > > world that every TEE (based on Arm TrustZone) will use to communicate
> > > with REE (Linux in our case) but rather an OP-TEE specific
> > > notifications feature that is built on top of OP-TEE specific ABIs.
> > >
> > > And I can see your arguments coming from an FFA perspective but there
> > > are platforms like the ones based on Armv7 which don't support FFA
> > > ABI. Maybe Jens can elaborate how this feature will fit in when FFA
> > > comes into picture?
> > >
> >
> > I can understand that but won't those platforms add the support both in
> > the kernel(current series) and secure world to address notifications.
> > While you could argue that it is small extension to what is already present
> > but I prefer they support FF-A is they need such a support instead of adding
> > custom mechanisms. It is hard to maintain and each vendor will deviate
> > from this custom mechanism and soon we will have bunch of them to handle.
>
> There exist armv7-a platforms that expect OP-TEE notification support and
> will not move the FF-A, like the stm32mp15. This platform won't move to FF-A
> mainly due to the memory cost of the added SPM layer and the device physical
> constraints.

Fair enough on the use-case and the analysis for not being able to use FF-A.
As you may already know it doesn't simply this problem. This has been
discussed for years and FF-A was assumed to be the solution when FF-A
spec work started.

> We have a usecase for OP-TEE notification. We're working on the integration
> of an SCMI server in OP-TEE. SCMI notification is a feature needed is this
> scope and it requires OP-TEE async notification means as those proposed
> here.
>

I am aware of this use-case, I understand. But I can only share rants
which I know doesn't help much.

> This OP-TEE async notif also brings a lot of value in OP-TEE as it allows a
> OP-TEE secure thread (i.e. executing a trusted application service) to
> gently wait on a secure interrupt (as a slow bus transaction completion or
> many other usecase) with the CPU relaxed. This support is provided by the
> proposed series. I believe existing device should be able to leverage this
> OP-TEE feature without needing their OP-TEE to move to the new FF-A
> interface.
>

While I agree these are nice to have in OPTEE, the timing is just odd.

We are trying hard to push FF-A as standard solution to address all such
issues that couldn't be solved with OPTEE + DT, now we are back to address
the same in parallel to FF-A.

--
Regards,
Sudeep

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-07-13 11:12 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-09  8:05 Etienne CARRIERE
2021-07-13 11:11 ` Sudeep Holla [this message]
2021-07-13 11:11   ` Sudeep Holla
2021-07-20  6:45   ` Jens Wiklander
2021-07-20  6:45     ` Jens Wiklander
2021-07-20  7:50     ` Sudeep Holla
2021-07-20  7:50       ` Sudeep Holla
2021-07-20  9:59       ` Jens Wiklander
2021-07-20  9:59         ` Jens Wiklander
  -- strict thread matches above, loose matches on Subject: below --
2021-06-16 10:36 Jens Wiklander
2021-06-16 10:36 ` Jens Wiklander
2021-06-17  4:33 ` Sumit Garg
2021-06-17  4:33   ` Sumit Garg
2021-06-17  6:10   ` Jens Wiklander
2021-06-17  6:10     ` Jens Wiklander
2021-07-06  7:25     ` Sumit Garg
2021-07-06  7:25       ` Sumit Garg
2021-07-06 10:36       ` Marc Zyngier
2021-07-06 10:36         ` Marc Zyngier
2021-07-06 11:39         ` Sumit Garg
2021-07-06 11:39           ` Sumit Garg
2021-07-06 12:46           ` Marc Zyngier
2021-07-06 12:46             ` Marc Zyngier
2021-07-07  5:52             ` Sumit Garg
2021-07-07  5:52               ` Sumit Garg
2021-07-07  6:54               ` Jens Wiklander
2021-07-07  6:54                 ` Jens Wiklander
2021-07-07 17:51               ` Sudeep Holla
2021-07-07 17:51                 ` Sudeep Holla
2021-07-08 12:56                 ` Sumit Garg
2021-07-08 12:56                   ` Sumit Garg

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