Re: [PATCH 1/2] KVM: arm64: add KVM_CAP_ARM_MP_AFFINITY extension

Andrew Jones
2020-09-17T07:39:22Z

On Thu, Sep 17, 2020 at 10:30:32AM +0800, Ying Fang wrote:
> Add KVM_CAP_ARM_MP_AFFINITY extension for userspace to check
> whether KVM supports setting MPIDR on AArch64 platform. Thus
> we can give userspace control over the MPIDR to present
> cpu topology information.
>
> Signed-off-by: Ying Fang <fangying1@huawei.com>
> ---
> Documentation/virt/kvm/api.rst | 8 ++++++++
> arch/arm64/kvm/arm.c | 1 +
> include/uapi/linux/kvm.h | 1 +
> 3 files changed, 10 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index eb3a1316f03e..d2fb18613a34 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6159,3 +6159,11 @@ KVM can therefore start protected VMs.
> This capability governs the KVM_S390_PV_COMMAND ioctl and the
> KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected
> guests when the state change is invalid.
> +
> +8.24 KVM_CAP_ARM_MP_AFFINITY
> +----------------------------
> +
> +:Architecture: arm64
> +
> +This capability indicates that KVM_ARM_SET_MP_AFFINITY ioctl is available.
> +It is used by to set MPIDR from userspace.
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 46dc3d75cf13..913c8da539b3 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -178,6 +178,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_ARM_IRQ_LINE_LAYOUT_2:
> case KVM_CAP_ARM_NISV_TO_USER:
> case KVM_CAP_ARM_INJECT_EXT_DABT:
> + case KVM_CAP_ARM_MP_AFFINITY:
> r = 1;

Caps should only return 1 after, or at the same time as, the feature is
introduced, otherwise bisection is broken.

> break;
> case KVM_CAP_ARM_SET_DEVICE_ADDR:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index f6d86033c4fa..c4874905cd9c 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1035,6 +1035,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_LAST_CPU 184
> #define KVM_CAP_SMALLER_MAXPHYADDR 185
> #define KVM_CAP_S390_DIAG318 186
> +#define KVM_CAP_ARM_MP_AFFINITY 187
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> --
> 2.23.0
>

Thanks,
drew