Re: [PATCH v19 15/20] KVM: arm64: CCA: Introduce Realms

[Gavin Shan <gshan@redhat.com>]

On 9/21/26 7:28 AM, Suzuki K Poulose wrote:
> From: Steven Price <steven.price@arm.com>
> 
> Add foundational work for supporting Realms.
>   - Add a new VM flavor.
>   - At KVM init, check if the KVM can support Realms (though not functional yet)
>     and will be advertised by static key kvm_rmi_is_available. This will be
>     turned on in a later patches, once we have all the bits and pieces ready.
>     For now check if we are blessed with KVM_MODE_RMM.
>   - Add realm specific tracking in kvm_arch. Since Realm and protected pKVM
>     states are mutually exclusive, move them into a union.
> 
> Please note that we cannot create Realm VMs yet. This requires further changes
> to the UABI and core RMI driver support, which will come later.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> Changes since v16:
>   * Share mutually exclusive pKVM and Realm per-VM storage in a union.
>   * Move to the new VM flavor infrastructure, split bits out. Trimmed down
>   * Move in Realm state and basic boiler plates
> Changes since v13:
>   * Most of the init has been moved out of the 'kvm' directory so this is
>     much more basic now.
> Changes since v12:
>   * Drop check for 4k page size.
> Changes since v11:
>   * Reword slightly the comments on the realm states.
> Changes since v10:
>   * kvm_is_realm() no longer has a NULL check.
>   * Rename from "rme" to "rmi" when referring to the RMM interface.
>   * Check for RME (hardware) support before probing for RMI support.
> Changes since v8:
>   * No need to guard kvm_init_rme() behind 'in_hyp_mode'.
> Changes since v6:
>   * Improved message for an unsupported RMI ABI version.
> Changes since v5:
>   * Reword "unsupported" message from "host supports" to "we want" to
>     clarify that 'we' are the 'host'.
> Changes since v2:
>   * Drop return value from kvm_init_rme(), it was always 0.
>   * Rely on the RMM return value to identify whether the RSI ABI is
>     compatible.
> ---
>   arch/arm64/include/asm/kvm_emulate.h | 16 ++++++++
>   arch/arm64/include/asm/kvm_host.h    | 18 +++++---
>   arch/arm64/include/asm/kvm_rmi.h     | 61 ++++++++++++++++++++++++++++
>   arch/arm64/include/asm/virt.h        |  1 +
>   arch/arm64/kvm/Makefile              |  2 +-
>   arch/arm64/kvm/arm.c                 |  6 +++
>   arch/arm64/kvm/mmu.c                 |  1 +
>   arch/arm64/kvm/rmi.c                 | 18 ++++++++
>   8 files changed, 117 insertions(+), 6 deletions(-)
>   create mode 100644 arch/arm64/include/asm/kvm_rmi.h
>   create mode 100644 arch/arm64/kvm/rmi.c
> 
Reviewed-by: Gavin Shan <gshan@redhat.com>