Re: [PATCH 5/9] KVM: s390: pv: Add query dump information

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

On 5/9/22 17:28, Claudio Imbrenda wrote:
> On Thu, 28 Apr 2022 13:00:58 +0000
> Janosch Frank <frankja@linux.ibm.com> wrote:
> 
>> The dump API requires userspace to provide buffers into which we will
>> store data. The dump information added in this patch tells userspace
>> how big those buffers need to be.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
>>   arch/s390/kvm/kvm-s390.c | 11 +++++++++++
>>   include/uapi/linux/kvm.h | 12 +++++++++++-
>>   2 files changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 23352d45a386..e327a5b8ef78 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -2255,6 +2255,17 @@ static ssize_t kvm_s390_handle_pv_info(struct kvm_s390_pv_info *info)
>>   
>>   		return len_min;
>>   	}
>> +	case KVM_PV_INFO_DUMP: {
>> +		len_min =  sizeof(info->header) + sizeof(info->dump);
> 
> so the output will have some zero-padded stuff at the end?

In which situation?

> 
>> +
>> +		if (info->header.len_max < len_min)
>> +			return -EINVAL;
>> +
>> +		info->dump.dump_cpu_buffer_len = uv_info.guest_cpu_stor_len;
>> +		info->dump.dump_config_mem_buffer_per_1m = uv_info.conf_dump_storage_state_len;
>> +		info->dump.dump_config_finalize_len = uv_info.conf_dump_finalize_len;
>> +		return len_min;
>> +	}
>>   	default:
>>   		return -EINVAL;
>>   	}
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 59e4fb6c7a34..2eba89d7ec29 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1647,6 +1647,13 @@ struct kvm_s390_pv_unp {
>>   
>>   enum pv_cmd_info_id {
>>   	KVM_PV_INFO_VM,
>> +	KVM_PV_INFO_DUMP,
>> +};
>> +
>> +struct kvm_s390_pv_info_dump {
>> +	__u64 dump_cpu_buffer_len;
>> +	__u64 dump_config_mem_buffer_per_1m;
>> +	__u64 dump_config_finalize_len;
>>   };
>>   
>>   struct kvm_s390_pv_info_vm {
>> @@ -1666,7 +1673,10 @@ struct kvm_s390_pv_info_header {
>>   
>>   struct kvm_s390_pv_info {
>>   	struct kvm_s390_pv_info_header header;
>> -	struct kvm_s390_pv_info_vm vm;
>> +	union {
>> +		struct kvm_s390_pv_info_dump dump;
>> +		struct kvm_s390_pv_info_vm vm;
>> +	};
>>   };
>>   
>>   enum pv_cmd_id {
>