Re: [PATCH v5 00/12] GenieZone hypervisor drivers - Yi-De Wu (吳一德)

From: "Yi-De Wu (吳一德)" <Yi-De.Wu@mediatek.com>
To: "robh@kernel.org" <robh@kernel.org>
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Subject: Re: [PATCH v5 00/12] GenieZone hypervisor drivers
Date: Thu, 31 Aug 2023 08:09:43 +0000	[thread overview]
Message-ID: <62be4ec46d685cc411a5b38d9710f99be2a15239.camel@mediatek.com> (raw)
In-Reply-To: <4b81b7fbd50c04958c27fbb6e620a15ae4fe0d54.camel@mediatek.com>

On Thu, 2023-08-17 at 15:31 +0800, Yi-De Wu wrote:
> On Fri, 2023-08-11 at 10:52 -0600, Rob Herring wrote:
> >  	 
> > External email : Please do not click links or open attachments
> > until
> > you have verified the sender or the content.
> >  On Thu, Jul 27, 2023 at 03:59:53PM +0800, Yi-De Wu wrote:
> > > This series is based on linux-next, tag: next-20230726.
> > > 
> > > GenieZone hypervisor(gzvm) is a type-1 hypervisor that supports
> > 
> > various virtual
> > > machine types and provides security features such as TEE-like
> > 
> > scenarios and
> > > secure boot. It can create guest VMs for security use cases and
> > > has
> > > virtualization capabilities for both platform and interrupt.
> > 
> > Although the
> > > hypervisor can be booted independently, it requires the
> > > assistance
> > 
> > of GenieZone
> > > hypervisor kernel driver(gzvm-ko) to leverage the ability of
> > > Linux
> > 
> > kernel for
> > > vCPU scheduling, memory management, inter-VM communication and
> > 
> > virtio backend
> > > support.
> > > 
> > > Changes in v5:
> > > - Add dt solution back for device initialization
> > 
> > Why? It's a software interface that you define and control. Make
> > that 
> > interface discoverable.
> > 
> > Rob
> 
> hi Rob,
> 
> Let me recap a bit about this as you might not notice our previous
> response[1]. In order to discover our GenieZone hypervisor, there
> were
> 2 solutions being talked about, namely with dt or without dt.
> 
> The reasons we use dt now were listed in some previous mail
> thread[2].
> I'll just copy the statements here for better sync-up.
> - Although dt is for hardware, it's difficult to discover a specific
> hypervisor without probing on all subsystem and thus pollute all of
> other users as a consequence.
> - The GenieZone hypervisor could be considered as a vendor model to
> assist platform virtualization whose implementation is independent
> from
> Linuxism.
> 
> In contrast to the solution with dt, what we were doing was probing
> via
> hypercall to see whether our hypervisor exists.
> However, this could raise some concerns about "polluting all systems"
> even for those systems without GenieZone hypervisor embedded[3].
> 
> We're wondering if there's any specific implementation in mind from
> your side that we could initialize our device in a discoverable
> manners
> while not affecting other systems. We'll appreciate for the hint.
> 
> Regards,
> 
> Reference
> 1. 
> 
https://lore.kernel.org/all/14c0381be38ea40fcd03104bff32bcaa09b920d3.camel@mediatek.com/
> 2. 
> 
https://lore.kernel.org/lkml/ea531ba80db67cccb03ea173e714fe868f869e91.camel@mediatek.com/
> 3. 
> 
https://lore.kernel.org/all/2fe0c7f9-55fc-ae63-3631-8526a0212ccd@linaro.org/
> 
> 
> Regards,

A gentle ping.

We suppose a simple dt would be a consise solution here to initialize
the GenieZone hypervisor. We also found some other software pieces use
dt as well[4]. Perhaps it could be brought into discussion that dt
shall be suitable under our use case.

Reference
4. OP-TEE Trusted OS maintained by Linaro

https://elixir.bootlin.com/linux/v6.1/source/Documentation/devicetree/bindings/arm/firmware/tlm,trusted-foundations.yaml