Re: [PATCH v19 19/20] KVM: arm64: CCA: Expose SVE VL register before VCPU finalization

[Gavin Shan]

On 9/21/26 7:28 AM, Suzuki K Poulose wrote:
> From: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
>
> Userspace must configure the SVE vector length before the Realm is created
> (as it is part of the parameter for Realm creation), but the Realm VCPUs
> cannot be finalized until after the Realm Descriptor has been created.
>
> KVM_GET_REG_LIST currently rejects the unfinalized VCPUs, which prevents
> the userspace from discovering and configuring the VLs for  the Realm.
>
> Allow KVM_GET_REG_LIST for unfinalized RECs and make the SVE register
> enumeration handle the unfinalized case explicitly. i.e., only expose
> KVM_REG_ARM64_SVE_VLS before SVE is finalized.
>
> One adverse side effect of this change is that a KVM_GET_REG_LIST call that
> only probes for the array size will now succeed even if SVE is not
> finalized, but that seems harmless since the following KVM_GET_REG_LIST
> with the full array will fail.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> Changes since v17:
>   - Rewrite the commit description to clearly describe the purpose
> ---
>   arch/arm64/kvm/arm.c   | 15 ++++++++++++++-
>   arch/arm64/kvm/guest.c | 10 +++++-----
>   2 files changed, 19 insertions(+), 6 deletions(-)

Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>