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From: Marc Zyngier <maz@kernel.org>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: 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 List <devicetree@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Jerome Forissier <jerome@forissier.org>,
	Etienne Carriere <etienne.carriere@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH v2 0/7] Asynchronous notifications from secure world
Date: Tue, 06 Jul 2021 11:36:17 +0100	[thread overview]
Message-ID: <87czrv91b2.wl-maz@kernel.org> (raw)
In-Reply-To: <CAFA6WYMSAM2MDOXnhjuZFov3BtF8-nihZRUpR8ciUWsL4_nCWA@mail.gmail.com>

On Tue, 06 Jul 2021 08:25:26 +0100,
Sumit Garg <sumit.garg@linaro.org> wrote:
> 
> On Thu, 17 Jun 2021 at 11:40, Jens Wiklander <jens.wiklander@linaro.org> wrote:
> >
> > Hi Sumit,
> >
> > On Thu, Jun 17, 2021 at 6:33 AM Sumit Garg <sumit.garg@linaro.org> wrote:
> > >
> > > Hi Jens,
> > >
> > > On Wed, 16 Jun 2021 at 16:07, Jens Wiklander <jens.wiklander@linaro.org> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > This adds support for asynchronous notifications from OP-TEE in secure
> > > > world to the OP-TEE driver. This allows a design with a top half and bottom
> > > > half type of driver where the top half runs in secure interrupt context and
> > > > a notifications tells normal world to schedule a yielding call to do the
> > > > bottom half processing.
> > > >
> > > > An interrupt is used to notify the driver that there are asynchronous
> > > > notifications pending.
> > > >
> > >
> > > It looks like a nice feature. I would like to get hands on with this.
> > > Can I test this feature on Qemu?
> >
> > Absolutely, you can get this into the normal OP-TEE development repo setup with:
> > repo init -u https://github.com/OP-TEE/manifest.git -m default.xml
> > repo sync
> > Update optee_os with
> > https://github.com/jenswi-linaro/optee_os/tree/async_notif_v2
> > Update linux with https://github.com/jenswi-linaro/linux-1/tree/async_notif_v2
> > cd build
> > make all -j...
> > make run-only
> >
> > If you type anything at the secure console you'll notice how it
> > changes behaviour once the Linux kernel has booted.
> >
> 
> Thanks for sharing instructions as I now got some time to test and
> deep dive into this feature. It looks like a pretty useful feature to
> realize interrupt support in the secure world in its true sense. This
> feature works for me as per your instructions.
> 
> I could recognise it's requirement from the time while I was playing
> with secure timer interrupt support for OP-TEE RNG driver on
> Developerbox. In that case I had to strip down the secure interrupt
> handler to a minimum that would just collect entropy and dump into the
> secure buffer. But with asynchronous notifications support, I could
> add more functionality like entropy health tests in the bottom half
> instead of doing those health tests while retrieving entropy from the
> secure world.
> 
> Given that, have you explored the possibility to leverage SGI rather
> than a platform specific SPI for notifying the normal world? If it's
> possible to leverage Architecture specific SGI for this purpose then I

What does "Architecture specific SGI" mean?

> think this feature will come automatically enabled for every platform
> without the need to reserve a platform specific SPI.

That old chestnut again...

- How do you discover that the secure side has graced you with a
  Group-1 SGI (no, you can't use one of the first 8)? for both DT and
  ACPI?

- How do you find which CPUs are targeted by this SGI? All? One? A
  subset? What is the expected behaviour with CPU hotplug? How can the
  NS side (Linux) can inform the secure side about the CPUs it wants
  to use?

- Is there any case where you would instead need a level interrupt
  (which a SGI cannot provide)?

In general, cross world SGIs are a really bad idea. Yes, some people
like them. I still think they are misguided, and I don't intend to
provide a generic request interface for this.

	M.

-- 
Without deviation from the norm, progress is not possible.

WARNING: multiple messages have this Message-ID
From: Marc Zyngier <maz@kernel.org>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: 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 List <devicetree@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Jerome Forissier <jerome@forissier.org>,
	Etienne Carriere <etienne.carriere@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH v2 0/7] Asynchronous notifications from secure world
Date: Tue, 06 Jul 2021 11:36:17 +0100	[thread overview]
Message-ID: <87czrv91b2.wl-maz@kernel.org> (raw)
In-Reply-To: <CAFA6WYMSAM2MDOXnhjuZFov3BtF8-nihZRUpR8ciUWsL4_nCWA@mail.gmail.com>

On Tue, 06 Jul 2021 08:25:26 +0100,
Sumit Garg <sumit.garg@linaro.org> wrote:
> 
> On Thu, 17 Jun 2021 at 11:40, Jens Wiklander <jens.wiklander@linaro.org> wrote:
> >
> > Hi Sumit,
> >
> > On Thu, Jun 17, 2021 at 6:33 AM Sumit Garg <sumit.garg@linaro.org> wrote:
> > >
> > > Hi Jens,
> > >
> > > On Wed, 16 Jun 2021 at 16:07, Jens Wiklander <jens.wiklander@linaro.org> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > This adds support for asynchronous notifications from OP-TEE in secure
> > > > world to the OP-TEE driver. This allows a design with a top half and bottom
> > > > half type of driver where the top half runs in secure interrupt context and
> > > > a notifications tells normal world to schedule a yielding call to do the
> > > > bottom half processing.
> > > >
> > > > An interrupt is used to notify the driver that there are asynchronous
> > > > notifications pending.
> > > >
> > >
> > > It looks like a nice feature. I would like to get hands on with this.
> > > Can I test this feature on Qemu?
> >
> > Absolutely, you can get this into the normal OP-TEE development repo setup with:
> > repo init -u https://github.com/OP-TEE/manifest.git -m default.xml
> > repo sync
> > Update optee_os with
> > https://github.com/jenswi-linaro/optee_os/tree/async_notif_v2
> > Update linux with https://github.com/jenswi-linaro/linux-1/tree/async_notif_v2
> > cd build
> > make all -j...
> > make run-only
> >
> > If you type anything at the secure console you'll notice how it
> > changes behaviour once the Linux kernel has booted.
> >
> 
> Thanks for sharing instructions as I now got some time to test and
> deep dive into this feature. It looks like a pretty useful feature to
> realize interrupt support in the secure world in its true sense. This
> feature works for me as per your instructions.
> 
> I could recognise it's requirement from the time while I was playing
> with secure timer interrupt support for OP-TEE RNG driver on
> Developerbox. In that case I had to strip down the secure interrupt
> handler to a minimum that would just collect entropy and dump into the
> secure buffer. But with asynchronous notifications support, I could
> add more functionality like entropy health tests in the bottom half
> instead of doing those health tests while retrieving entropy from the
> secure world.
> 
> Given that, have you explored the possibility to leverage SGI rather
> than a platform specific SPI for notifying the normal world? If it's
> possible to leverage Architecture specific SGI for this purpose then I

What does "Architecture specific SGI" mean?

> think this feature will come automatically enabled for every platform
> without the need to reserve a platform specific SPI.

That old chestnut again...

- How do you discover that the secure side has graced you with a
  Group-1 SGI (no, you can't use one of the first 8)? for both DT and
  ACPI?

- How do you find which CPUs are targeted by this SGI? All? One? A
  subset? What is the expected behaviour with CPU hotplug? How can the
  NS side (Linux) can inform the secure side about the CPUs it wants
  to use?

- Is there any case where you would instead need a level interrupt
  (which a SGI cannot provide)?

In general, cross world SGIs are a really bad idea. Yes, some people
like them. I still think they are misguided, and I don't intend to
provide a generic request interface for this.

	M.

-- 
Without deviation from the norm, progress is not possible.

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

  reply	other threads:[~2021-07-06 10:36 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 10:36 Jens Wiklander
2021-06-16 10:36 ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 1/7] docs: staging/tee.rst: add a section on OP-TEE notifications Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 2/7] dt-bindings: arm: Convert optee binding to json-schema Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 16:03   ` Rob Herring
2021-06-16 16:03     ` Rob Herring
2021-06-16 16:05   ` Rob Herring
2021-06-16 16:05     ` Rob Herring
2021-06-22  8:38     ` Jens Wiklander
2021-06-22  8:38       ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 3/7] dt-bindings: arm: optee: add interrupt property Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 16:05   ` Rob Herring
2021-06-16 16:05     ` Rob Herring
2021-06-22  8:41     ` Jens Wiklander
2021-06-22  8:41       ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 4/7] tee: fix put order in teedev_close_context() Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 5/7] tee: add tee_dev_open_helper() primitive Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 6/7] optee: separate notification functions Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 10:36 ` [PATCH v2 7/7] optee: add asynchronous notifications Jens Wiklander
2021-06-16 10:36   ` Jens Wiklander
2021-06-16 14:08   ` Ard Biesheuvel
2021-06-16 14:08     ` Ard Biesheuvel
2021-06-17  4:33 ` [PATCH v2 0/7] Asynchronous notifications from secure world 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 [this message]
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
2021-07-09  8:05 Etienne CARRIERE
2021-07-13 11:11 ` Sudeep Holla
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

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