Re: [PATCH v5 03/10] KVM: s390: pv: Add query interface

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon, 16 May 2022 09:08:10 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:

> Some of the query information is already available via sysfs but
> having a IOCTL makes the information easier to retrieve.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/s390/kvm/kvm-s390.c | 76 ++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm.h | 25 +++++++++++++
>  2 files changed, 101 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 76ad6408cb2c..5859f243d287 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2224,6 +2224,42 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
>  	return r;
>  }
>  
> +/*
> + * Here we provide user space with a direct interface to query UV
> + * related data like UV maxima and available features as well as
> + * feature specific data.
> + *
> + * To facilitate future extension of the data structures we'll try to
> + * write data up to the maximum requested length.
> + */
> +static ssize_t kvm_s390_handle_pv_info(struct kvm_s390_pv_info *info)
> +{
> +	ssize_t len_min;
> +
> +	switch (info->header.id) {
> +	case KVM_PV_INFO_VM: {
> +		len_min =  sizeof(info->header) + sizeof(info->vm);
> +
> +		if (info->header.len_max < len_min)
> +			return -EINVAL;
> +
> +		memcpy(info->vm.inst_calls_list,
> +		       uv_info.inst_calls_list,
> +		       sizeof(uv_info.inst_calls_list));
> +
> +		/* It's max cpuid not max cpus, so it's off by one */
> +		info->vm.max_cpus = uv_info.max_guest_cpu_id + 1;
> +		info->vm.max_guests = uv_info.max_num_sec_conf;
> +		info->vm.max_guest_addr = uv_info.max_sec_stor_addr;
> +		info->vm.feature_indication = uv_info.uv_feature_indications;
> +
> +		return len_min;
> +	}
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
>  {
>  	int r = 0;
> @@ -2360,6 +2396,46 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
>  			     cmd->rc, cmd->rrc);
>  		break;
>  	}
> +	case KVM_PV_INFO: {
> +		struct kvm_s390_pv_info info = {};
> +		ssize_t data_len;
> +
> +		/*
> +		 * No need to check the VM protection here.
> +		 *
> +		 * Maybe user space wants to query some of the data
> +		 * when the VM is still unprotected. If we see the
> +		 * need to fence a new data command we can still
> +		 * return an error in the info handler.
> +		 */
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&info, argp, sizeof(info.header)))
> +			break;
> +
> +		r = -EINVAL;
> +		if (info.header.len_max < sizeof(info.header))
> +			break;
> +
> +		data_len = kvm_s390_handle_pv_info(&info);
> +		if (data_len < 0) {
> +			r = data_len;
> +			break;
> +		}
> +		/*
> +		 * If a data command struct is extended (multiple
> +		 * times) this can be used to determine how much of it
> +		 * is valid.
> +		 */
> +		info.header.len_written = data_len;
> +
> +		r = -EFAULT;
> +		if (copy_to_user(argp, &info, data_len))
> +			break;
> +
> +		r = 0;
> +		break;
> +	}
>  	default:
>  		r = -ENOTTY;
>  	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 6a184d260c7f..8ac9de7d1386 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1653,6 +1653,30 @@ struct kvm_s390_pv_unp {
>  	__u64 tweak;
>  };
>  
> +enum pv_cmd_info_id {
> +	KVM_PV_INFO_VM,
> +};
> +
> +struct kvm_s390_pv_info_vm {
> +	__u64 inst_calls_list[4];
> +	__u64 max_cpus;
> +	__u64 max_guests;
> +	__u64 max_guest_addr;
> +	__u64 feature_indication;
> +};
> +
> +struct kvm_s390_pv_info_header {
> +	__u32 id;
> +	__u32 len_max;
> +	__u32 len_written;
> +	__u32 reserved;
> +};
> +
> +struct kvm_s390_pv_info {
> +	struct kvm_s390_pv_info_header header;
> +	struct kvm_s390_pv_info_vm vm;
> +};
> +
>  enum pv_cmd_id {
>  	KVM_PV_ENABLE,
>  	KVM_PV_DISABLE,
> @@ -1661,6 +1685,7 @@ enum pv_cmd_id {
>  	KVM_PV_VERIFY,
>  	KVM_PV_PREP_RESET,
>  	KVM_PV_UNSHARE_ALL,
> +	KVM_PV_INFO,
>  };
>  
>  struct kvm_pv_cmd {