Re: [PATCH v5 30/33] KVM: PPC: Book3S HV: Allow HV module to load without hypervisor mode

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Oct 08, 2018 at 04:31:16PM +1100, Paul Mackerras wrote:
> With this, the KVM-HV module can be loaded in a guest running under
> KVM-HV, and if the hypervisor supports nested virtualization, this
> guest can now act as a nested hypervisor and run nested guests.
> 
> This also adds some checks to inform userspace that HPT guests are not
> supported by nested hypervisors (by returning false for the
> KVM_CAP_PPC_MMU_HASH_V3 capability), and to prevent userspace from
> configuring a guest to use HPT mode.
> 
> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  arch/powerpc/kvm/book3s_hv.c | 16 ++++++++++++----
>  arch/powerpc/kvm/powerpc.c   |  3 ++-
>  2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 127bb5f..152bf75 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4807,11 +4807,15 @@ static int kvmppc_core_emulate_mfspr_hv(struct kvm_vcpu *vcpu, int sprn,
>  
>  static int kvmppc_core_check_processor_compat_hv(void)
>  {
> -	if (!cpu_has_feature(CPU_FTR_HVMODE) ||
> -	    !cpu_has_feature(CPU_FTR_ARCH_206))
> -		return -EIO;
> +	if (cpu_has_feature(CPU_FTR_HVMODE) &&
> +	    cpu_has_feature(CPU_FTR_ARCH_206))
> +		return 0;
>  
> -	return 0;
> +	/* POWER9 in radix mode is capable of being a nested hypervisor. */
> +	if (cpu_has_feature(CPU_FTR_ARCH_300) && radix_enabled())
> +		return 0;
> +
> +	return -EIO;
>  }
>  
>  #ifdef CONFIG_KVM_XICS
> @@ -5129,6 +5133,10 @@ static int kvmhv_configure_mmu(struct kvm *kvm, struct kvm_ppc_mmuv3_cfg *cfg)
>  	if (radix && !radix_enabled())
>  		return -EINVAL;
>  
> +	/* If we're a nested hypervisor, we currently only support radix */
> +	if (kvmhv_on_pseries() && !radix)
> +		return -EINVAL;
> +
>  	mutex_lock(&kvm->lock);
>  	if (radix != kvm_is_radix(kvm)) {
>  		if (kvm->arch.mmu_ready) {
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index eba5756..1f4b128 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -594,7 +594,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  		r = !!(hv_enabled && radix_enabled());
>  		break;
>  	case KVM_CAP_PPC_MMU_HASH_V3:
> -		r = !!(hv_enabled && cpu_has_feature(CPU_FTR_ARCH_300));
> +		r = !!(hv_enabled && cpu_has_feature(CPU_FTR_ARCH_300) &&
> +		       cpu_has_feature(CPU_FTR_HVMODE));
>  		break;
>  #endif
>  	case KVM_CAP_SYNC_MMU:

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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