[RFC PATCH v1 1/2] KVM: arm64: CCA: Add support for configuring the Realm MEC policy

[Kohei Enju]

Hi Suzuki,

I sent the message below off-list a few weeks ago, but I'm following up
on-list in case it didn't reach you.

Since then, I've started reworking the series based on the
kvm_device_attr approach you suggested, and I'm currently testing it
against v23 of the CCA host support.

I'd still appreciate any feedback on the ABI direction, as well as
whether you see any concerns with posting the RFC series while the host
support is not yet upstream.

Thanks,
Kohei

On Fri, Oct 9, 2026 at 03:15:23PM +0900, Kohei Enju wrote:
> On 07/31 14:09, Kohei Enju wrote:
> > On 07/29 12:47, Suzuki K Poulose wrote:
> > > Hello
> > > 
> > > Thanks for sending the patch. Please find my comments inline below.
> > > 
> > > 
> > > On 24/07/2026 10:40, Kohei Enju wrote:
> > > > Introduce the KVM_ARM_RMI_CONFIG ioctl to allow userspace to configure
> > > > Realm VM parameters before the Realm is created.
> > > 
> > > This approach is something we tried in the past. Another option is to
> > > add these as kvm_device_attr for the KVM VM, under a new group, e.g.,
> > > KVM_ARM_VM_RMI_CTRL and add the following attributes :
> > > 
> > > KVM_ARM_VM_RMI_CTRL_RPV 		-> Realm Personalization Value
> > > KVM_ARM_VM_RMI_CTRL_MEASUREMENT_ALGO	-> Measuerment algo
> > > KVM_ARM_VM_RMI_CTRL_MEC_PRIVATE		-> Private MEC Policy. By default to shared
> > > ?
> > 
> > Hi Suzuki, thanks for suggesting another option. That looks good to me,
> > and I'd be happy with either approach.
> > Anyway I'd like to wait for feedback from the maintainers and other
> > reviewers.
> 
> Hi Suzuki,
> 
> I'm thinking of respinning the MEC policy series as RFC v2, as you
> mentioned in the Core Collective WG last month.
> 
> For the ABI, I'm planning to switch to the kvm_device_attr-based
> approach you suggested instead of introducing a new VM ioctl. Before I
> start reworking the series, do you have any concerns with that
> direction?
> 
> One other point is that the series still depends on the CCA host
> support, which is not upstream yet. As a result, tools such as Sashiko
> would likely be unable to identify the correct base tree and may not be
> able to provide useful automated review feedback.
> 
> Personally, I think this is acceptable since the series is still RFC and
> the primary goal is to get feedback on the ABI and overall design rather
> than seeking integration at this stage. However, I am aware that posting
> patches on top of non-upstream trees can sometimes be problematic from a
> review perspective.
> 
> Do you have any concerns about posting an RFC series in this situation,
> or would you prefer that I wait until the host support lands upstream?
> 
> Thanks,
> Kohei