Re: [PATCH 3/9] KVM: s390: pv: Add query interface

[Thomas Huth <thuth@redhat.com>]

On 23/02/2022 10.20, Janosch Frank 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>
> ---
>   arch/s390/kvm/kvm-s390.c | 47 ++++++++++++++++++++++++++++++++++++++++
>   include/uapi/linux/kvm.h | 23 ++++++++++++++++++++
>   2 files changed, 70 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index faa85397b6fb..837f898ad2ff 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2217,6 +2217,34 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
>   	return r;
>   }
>   
> +static int kvm_s390_handle_pv_info(struct kvm_s390_pv_info *info)
> +{
> +	u32 len;
> +
> +	switch (info->header.id) {
> +	case KVM_PV_INFO_VM: {
> +		len =  sizeof(info->header) + sizeof(info->vm);
> +
> +		if (info->header.len < len)
> +			return -EINVAL;
> +
> +		memcpy(info->vm.inst_calls_list,
> +		       uv_info.inst_calls_list,
> +		       sizeof(uv_info.inst_calls_list));
> +
> +		/* It's max cpuidm 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 0;
> +	}
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>   static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
>   {
>   	int r = 0;
> @@ -2353,6 +2381,25 @@ 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 = {};
> +
> +		if (copy_from_user(&info, argp, sizeof(info.header)))
> +			return -EFAULT;
> +
> +		if (info.header.len < sizeof(info.header))
> +			return -EINVAL;
> +
> +		r = kvm_s390_handle_pv_info(&info);
> +		if (r)
> +			return r;
> +
> +		r = copy_to_user(argp, &info, sizeof(info));

sizeof(info) is currently OK ... but this might break if somebody later 
extends the kvm_s390_pv_info struct, I guess? ==> Maybe also better use 
sizeof(info->header) + sizeof(info->vm) here, too? Or let 
kvm_s390_handle_pv_info() return the amount of bytes that should be copied here?

  Thomas


> +		if (r)
> +			return -EFAULT;
> +		return 0;
> +	}
>   	default:
>   		r = -ENOTTY;
>   	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index dbc550bbd9fa..96fceb204a92 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1642,6 +1642,28 @@ 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;
> +};
> +
> +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,
> @@ -1650,6 +1672,7 @@ enum pv_cmd_id {
>   	KVM_PV_VERIFY,
>   	KVM_PV_PREP_RESET,
>   	KVM_PV_UNSHARE_ALL,
> +	KVM_PV_INFO,
>   };
>   
>   struct kvm_pv_cmd {