Re: [PATCH V4] xen/vm_event: Clean up control-register-write vm_events

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

On 05/22/2015 10:36 AM, Jan Beulich wrote:
>> @@ -1050,6 +1048,8 @@ struct xen_domctl_monitor_op {
>>       */
>>      union {
>>          struct {
>> +            /* Which control register */
>> +            uint8_t index;
> 
> Okay, 8 bits here (which is reasonable), but ...
> 
>> @@ -156,7 +158,8 @@ struct vm_event_mem_access {
>>      uint32_t _pad;
>>  };
>>  
>> -struct vm_event_mov_to_cr {
>> +struct vm_event_write_ctrlreg {
>> +    uint64_t index;
>>      uint64_t new_value;
>>      uint64_t old_value;
>>  };
> 
> ... a full 64 bits here? 32 bits surely would do (with 32 bits of padding),
> allowing slightly better accessing code on both the consumer and
> producer sides.

While working on this I found the following in the vm_event.h header:

168 struct vm_event_debug {
169     uint64_t gfn;
170     uint32_t _pad;
171 };

Is this supposed to be 64 + 32 bits padding?


Thanks,
Razvan