[PATCH 00/14] KVM: arm64: NV userspace ABI

[Oliver Upton]

On Sat, Feb 15, 2025 at 05:38:02PM +0000, Marc Zyngier wrote:
> Since the previous incarnation of the ABI was proved to be subtly
> wrong, I have reworked it to be more in line with the current way KVM
> operates.
> 
> No more late NV-specific adjustment nor writable ID_AA64MMFR0_EL1.VH.
> The NV configuration is now entirely selected from the vcpu flags.
> I've preserved the KVM_ARM_VCPU_EL2 flag which enables NV with VHE,
> and added KVM_ARM_VCPU_EL2_E2H0 which alters the NV behaviour to only
> allow nVHE guests without recursive NV support.
> 
> This series is actually very little new code. The bulk of it is
> converting the feature downgrade to be per-idreg, essentially going
> back to the state before 44241f34fac96 ("KVM: arm64: nv: Use accessors
> for modifying ID registers"), only slightly modernised. This then
> becomes part of the reset value computing.
> 
> The rest is simply what you'd expect in terms of being able to write
> the ID_AA64MMFR4_EL1.NV_frac field, making the correct bits RES0 when
> needed, probing for capabilities and handling the init flags.
> 
> Patches on top of -rc2, with the integration branch at the usual
> location.

This all looks reasonable to me. NV won't be ready for the limelight
this time around so unless someone shouts I plan on taking the first 12
patches of this series in 6.15.

Thanks,
Oliver