Introduce a new capability and ioctl to expose CPU compatibility modes supported by the host processor for nested guests.
Introduce a new KVM capability, KVM_CAP_PPC_COMPAT_CAPS, and a corresponding vm ioctl, KVM_PPC_GET_COMPAT_CAPS, to expose processor compatibility modes supported by the host. On IBM POWER systems, newer processor generations (N) can operate in compatibility modes corresponding to earlier generations, like (N-1) and (N-2). This is particularly relevant for nested virtualization, where nested KVM guests may need to run with a specific processor compatibility level. The new ioctl returns a bitmap describing the compatibility modes supported by the host in respective bit numbers. This allows userspace to select an appropriate compatibility level when configuring nested KVM guests. Signed-off-by: Amit Machhiwal <[email protected]> --- arch/powerpc/include/uapi/asm/kvm.h | 6 ++++++ include/uapi/linux/kvm.h | 4 ++++ 2 files changed, 10 insertions(+) diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h index 077c5437f521..a38dff7a8aea 100644 --- a/arch/powerpc/include/uapi/asm/kvm.h +++ b/arch/powerpc/include/uapi/asm/kvm.h @@ -437,6 +437,12 @@ struct kvm_ppc_cpu_char { __u64 behaviour_mask; /* valid bits in behaviour */ }; +/* For KVM_PPC_GET_COMPAT_CAPS */ +struct kvm_ppc_compat_caps { + __u32 flags; + __u64 compat_capabilities; /* Capabilities supported by the host */ +}; + /* * Values for character and character_mask. * These are identical to the values used by H_GET_CPU_CHARACTERISTICS. diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 6c8afa2047bf..1788a0068662 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -996,6 +996,7 @@ struct kvm_enable_cap { #define KVM_CAP_S390_USER_OPEREXEC 246 #define KVM_CAP_S390_KEYOP 247 #define KVM_CAP_S390_VSIE_ESAMODE 248 +#define KVM_CAP_PPC_COMPAT_CAPS 249 struct kvm_irq_routing_irqchip { __u32 irqchip; @@ -1349,6 +1350,9 @@ struct kvm_s390_keyop { #define KVM_GET_DEVICE_ATTR _IOW(KVMIO, 0xe2, struct kvm_device_attr) #define KVM_HAS_DEVICE_ATTR _IOW(KVMIO, 0xe3, struct kvm_device_attr) +/* Available with KVM_CAP_PPC_COMPAT_CAPS */ +#define KVM_PPC_GET_COMPAT_CAPS _IOR(KVMIO, 0xe4, struct kvm_ppc_compat_caps) + /* * ioctls for vcpu fds */ -- 2.50.1
