Re: [PATCH v5 32/33] KVM: PPC: Book3S HV: Add a VM capability to enable nested virtualization

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

[-- Attachment #1: Type: text/plain, Size: 7729 bytes --]

On Mon, Oct 08, 2018 at 04:31:18PM +1100, Paul Mackerras wrote:
> With this, userspace can enable a KVM-HV guest to run nested guests
> under it.
> 
> The administrator can control whether any nested guests can be run;
> setting the "nested" module parameter to false prevents any guests
> becoming nested hypervisors (that is, any attempt to enable the nested
> capability on a guest will fail).  Guests which are already nested
> hypervisors will continue to be so.
> 
> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

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

> ---
>  Documentation/virtual/kvm/api.txt  | 14 ++++++++++++++
>  arch/powerpc/include/asm/kvm_ppc.h |  1 +
>  arch/powerpc/kvm/book3s_hv.c       | 39 +++++++++++++++++++++++++++++---------
>  arch/powerpc/kvm/powerpc.c         | 12 ++++++++++++
>  include/uapi/linux/kvm.h           |  1 +
>  5 files changed, 58 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 2f5f9b7..fde48b6 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -4532,6 +4532,20 @@ With this capability, a guest may read the MSR_PLATFORM_INFO MSR. Otherwise,
>  a #GP would be raised when the guest tries to access. Currently, this
>  capability does not enable write permissions of this MSR for the guest.
>  
> +7.16 KVM_CAP_PPC_NESTED_HV
> +
> +Architectures: ppc
> +Parameters: none
> +Returns: 0 on success, -EINVAL when the implementation doesn't support
> +	 nested-HV virtualization.
> +
> +HV-KVM on POWER9 and later systems allows for "nested-HV"
> +virtualization, which provides a way for a guest VM to run guests that
> +can run using the CPU's supervisor mode (privileged non-hypervisor
> +state).  Enabling this capability on a VM depends on the CPU having
> +the necessary functionality and on the facility being enabled with a
> +kvm-hv module parameter.
> +
>  8. Other capabilities.
>  ----------------------
>  
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index 245e564..b3796bd 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -327,6 +327,7 @@ struct kvmppc_ops {
>  	int (*set_smt_mode)(struct kvm *kvm, unsigned long mode,
>  			    unsigned long flags);
>  	void (*giveup_ext)(struct kvm_vcpu *vcpu, ulong msr);
> +	int (*enable_nested)(struct kvm *kvm);
>  };
>  
>  extern struct kvmppc_ops *kvmppc_hv_ops;
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 152bf75..fa61647 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -118,6 +118,16 @@ module_param_cb(h_ipi_redirect, &module_param_ops, &h_ipi_redirect, 0644);
>  MODULE_PARM_DESC(h_ipi_redirect, "Redirect H_IPI wakeup to a free host core");
>  #endif
>  
> +/* If set, guests are allowed to create and control nested guests */
> +static bool nested = true;
> +module_param(nested, bool, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(nested, "Enable nested virtualization (only on POWER9)");
> +
> +static inline bool nesting_enabled(struct kvm *kvm)
> +{
> +	return kvm->arch.nested_enable && kvm_is_radix(kvm);
> +}
> +
>  /* If set, the threads on each CPU core have to be in the same MMU mode */
>  static bool no_mixing_hpt_and_radix;
>  
> @@ -959,12 +969,12 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
>  
>  	case H_SET_PARTITION_TABLE:
>  		ret = H_FUNCTION;
> -		if (vcpu->kvm->arch.nested_enable)
> +		if (nesting_enabled(vcpu->kvm))
>  			ret = kvmhv_set_partition_table(vcpu);
>  		break;
>  	case H_ENTER_NESTED:
>  		ret = H_FUNCTION;
> -		if (!vcpu->kvm->arch.nested_enable)
> +		if (!nesting_enabled(vcpu->kvm))
>  			break;
>  		ret = kvmhv_enter_nested_guest(vcpu);
>  		if (ret == H_INTERRUPT) {
> @@ -974,9 +984,8 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
>  		break;
>  	case H_TLB_INVALIDATE:
>  		ret = H_FUNCTION;
> -		if (!vcpu->kvm->arch.nested_enable)
> -			break;
> -		ret = kvmhv_do_nested_tlbie(vcpu);
> +		if (nesting_enabled(vcpu->kvm))
> +			ret = kvmhv_do_nested_tlbie(vcpu);
>  		break;
>  
>  	default:
> @@ -4496,10 +4505,8 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
>  /* Must be called with kvm->lock held and mmu_ready = 0 and no vcpus running */
>  int kvmppc_switch_mmu_to_hpt(struct kvm *kvm)
>  {
> -	if (kvm->arch.nested_enable) {
> -		kvm->arch.nested_enable = false;
> +	if (nesting_enabled(kvm))
>  		kvmhv_release_all_nested(kvm);
> -	}
>  	kvmppc_free_radix(kvm);
>  	kvmppc_update_lpcr(kvm, LPCR_VPM1,
>  			   LPCR_VPM1 | LPCR_UPRT | LPCR_GTSE | LPCR_HR);
> @@ -4776,7 +4783,7 @@ static void kvmppc_core_destroy_vm_hv(struct kvm *kvm)
>  
>  	/* Perform global invalidation and return lpid to the pool */
>  	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
> -		if (kvm->arch.nested_enable)
> +		if (nesting_enabled(kvm))
>  			kvmhv_release_all_nested(kvm);
>  		kvm->arch.process_table = 0;
>  		kvmhv_set_ptbl_entry(kvm->arch.lpid, 0, 0);
> @@ -5169,6 +5176,19 @@ static int kvmhv_configure_mmu(struct kvm *kvm, struct kvm_ppc_mmuv3_cfg *cfg)
>  	return err;
>  }
>  
> +static int kvmhv_enable_nested(struct kvm *kvm)
> +{
> +	if (!nested)
> +		return -EPERM;
> +	if (!cpu_has_feature(CPU_FTR_ARCH_300))
> +		return -ENODEV;
> +
> +	/* kvm == NULL means the caller is testing if the capability exists */
> +	if (kvm)
> +		kvm->arch.nested_enable = true;
> +	return 0;
> +}
> +
>  static struct kvmppc_ops kvm_ops_hv = {
>  	.get_sregs = kvm_arch_vcpu_ioctl_get_sregs_hv,
>  	.set_sregs = kvm_arch_vcpu_ioctl_set_sregs_hv,
> @@ -5208,6 +5228,7 @@ static struct kvmppc_ops kvm_ops_hv = {
>  	.configure_mmu = kvmhv_configure_mmu,
>  	.get_rmmu_info = kvmhv_get_rmmu_info,
>  	.set_smt_mode = kvmhv_set_smt_mode,
> +	.enable_nested = kvmhv_enable_nested,
>  };
>  
>  static int kvm_init_subcore_bitmap(void)
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 1f4b128..2869a29 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -597,6 +597,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  		r = !!(hv_enabled && cpu_has_feature(CPU_FTR_ARCH_300) &&
>  		       cpu_has_feature(CPU_FTR_HVMODE));
>  		break;
> +	case KVM_CAP_PPC_NESTED_HV:
> +		r = !!(hv_enabled && kvmppc_hv_ops->enable_nested &&
> +		       !kvmppc_hv_ops->enable_nested(NULL));
> +		break;
>  #endif
>  	case KVM_CAP_SYNC_MMU:
>  #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> @@ -2115,6 +2119,14 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>  			r = kvm->arch.kvm_ops->set_smt_mode(kvm, mode, flags);
>  		break;
>  	}
> +
> +	case KVM_CAP_PPC_NESTED_HV:
> +		r = -EINVAL;
> +		if (!is_kvmppc_hv_enabled(kvm) ||
> +		    !kvm->arch.kvm_ops->enable_nested)
> +			break;
> +		r = kvm->arch.kvm_ops->enable_nested(kvm);
> +		break;
>  #endif
>  	default:
>  		r = -EINVAL;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 251be35..d9cec6b 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -953,6 +953,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_NESTED_STATE 157
>  #define KVM_CAP_ARM_INJECT_SERROR_ESR 158
>  #define KVM_CAP_MSR_PLATFORM_INFO 159
> +#define KVM_CAP_PPC_NESTED_HV 160
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  

-- 
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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]