linux-kernel - Re: [PATCH v2 2/7] dt-bindings: hypervisor: Add MediaTek GenieZone hypervisor

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Message-ID: <14c0381be38ea40fcd03104bff32bcaa09b920d3.camel@mediatek.com>
Date:   Mon, 26 Jun 2023 09:05:17 +0000
From:   Yi-De Wu (吳一德) <Yi-De.Wu@...iatek.com>
To:     "robh@...nel.org" <robh@...nel.org>
CC:     "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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        MY Chuang (莊明躍) <MY.Chuang@...iatek.com>,
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        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
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        Shawn Hsiao (蕭志祥) 
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        Yingshiuan Pan (潘穎軒) 
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        Ivan Tseng (曾志軒) 
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Subject: Re: [PATCH v2 2/7] dt-bindings: hypervisor: Add MediaTek GenieZone
 hypervisor

On Fri, 2023-05-12 at 14:42 +0800, Yi-De Wu wrote:
> On Fri, 2023-04-28 at 16:24 -0500, Rob Herring wrote:
> > External email : Please do not click links or open attachments
> > until
> > you have verified the sender or the content.
> > 
> > 
> > On Fri, Apr 28, 2023 at 06:36:17PM +0800, Yi-De Wu wrote:
> > > From: "Yingshiuan Pan" <yingshiuan.pan@...iatek.com>
> > > 
> > > Add documentation for GenieZone(gzvm) node. This node informs
> > > gzvm
> > > driver to start probing if geniezone hypervisor is available and
> > > able to do virtual machine operations.
> > 
> > Why can't the driver just try and do virtual machine operations to
> > see
> > if the hypervisor is there? IOW, make your software interfaces
> > discoverable. DT is for non-discoverable hardware.
> > 
> > Rob
> 
> Can do, our hypervisor is discoverable through invoking probing
> hypercall, and we use the device tree to prevent unnecessary module
> loading on all systems.

hi Rob,

We'd like to continue with the argument whether to use dt here. As per
our previous discussion, we knew that dt is for non-discoverable
hardware. However, probing on all devices could possibly raise the
worries about polluting other users with redundant system overhead in
our v4 patches[1].

Are there any concerns from your side if we were to take the dt back in
v5 patches and keep it as simple as possible just to initialize our
hypervisor exclusively? Something similar to what we proposed
before[2].

Reference:
[1] 
https://lore.kernel.org/lkml/2fe0c7f9-55fc-ae63-3631-8526a0212ccd@linaro.org/
[2] 
https://android-review.googlesource.com/c/kernel/common/+/2447547/1..2/drivers/virt/geniezone/gzvm_main.c#b112

Regards,