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Date:   Thu, 11 Jun 2020 18:12:23 +0100
From:   Will Deacon <will@kernel.org>
To:     Achin Gupta <Achin.Gupta@arm.com>
Cc:     Rob Herring <robh@kernel.org>, Sudeep Holla <Sudeep.Holla@arm.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Marc Zyngier <maz@kernel.org>, nd <nd@arm.com>
Subject: Re: [RFC PATCH 1/3] dt-bindings: Add ARM PSA FF binding for
 non-secure VM partitions
Message-ID: <20200611171222.GB7725@willie-the-truck>
References: <20200601094512.50509-1-sudeep.holla@arm.com>
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 <20200609223551.GA1620273@bogus>
 <20200610074346.GB15939@willie-the-truck>
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On Thu, Jun 11, 2020 at 03:46:35PM +0000, Achin Gupta wrote:
> > On 10 Jun 2020, at 08:43, Will Deacon <will@kernel.org> wrote:
> > On Tue, Jun 09, 2020 at 04:35:51PM -0600, Rob Herring wrote:
> >> On Mon, Jun 01, 2020 at 10:45:10AM +0100, Sudeep Holla wrote:
> >>> Add devicetree bindings for a Arm PSA FF-A compliant non-secure partition
> >>> at virtual interface(VMs).
> >>> 
> >>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> >>> ---
> >>> .../devicetree/bindings/arm/arm,psa-ffa.txt   | 47 +++++++++++++++++++
> >>> 1 file changed, 47 insertions(+)
> >>> create mode 100644 Documentation/devicetree/bindings/arm/arm,psa-ffa.txt
> >> 
> >> I'm hoping this goes away if the firmware is discoverable, but if not DT 
> >> bindings are DT schema now.
> > 
> > We'll need the binding for the kvm host side, because there are plenty
> > of partition properties that are not discoverable (e.g. number of vCPUs).
> 
> Just trying to understand the req. a bit better…
> 
> The FF-A driver in the host can use FFA_PARTITION_INFO_GET to determine
> the count of partitions and their vCPUs.
> 
> Is this about a guest being able to find out how many vCPUs it has? 

This is about KVM finding out the information it needs in order to spawn
non-secure partitions. I don't see how it can do that with
FFA_PARTITION_INFO_GET -- who would respond?

But you're right that number of vCPUs was a bad example. We also need
information such as the entry point.

Will