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

[Janosch Frank <frankja@linux.ibm.com>]

On 5/9/22 17:25, Claudio Imbrenda wrote:
> On Thu, 28 Apr 2022 13:00:56 +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>
>> ---
>>   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..23352d45a386 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 cpuidm not max cpus so it's off by one */
> 
> s/cpuidm/cpuid,/ ? (and then also s/cpus/cpus,/)

Sure, will fix

> 
>> +		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 91a6fe4e02c0..59e4fb6c7a34 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1645,6 +1645,30 @@ 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,
>> @@ -1653,6 +1677,7 @@ enum pv_cmd_id {
>>   	KVM_PV_VERIFY,
>>   	KVM_PV_PREP_RESET,
>>   	KVM_PV_UNSHARE_ALL,
>> +	KVM_PV_INFO,
>>   };
>>   
>>   struct kvm_pv_cmd {
>