Re: [Xen-devel] [PATCH V5 07/12] xen: Introduce monitor_op domctl

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Tue, Feb 17, 2015 at 7:37 PM, Andrew Cooper
<andrew.cooper3@xxxxxxxxxx> wrote:
> On 17/02/15 18:20, Tamas K Lengyel wrote:
>> +/************************************************/
>> +/*            monitor event options             */
>> +/************************************************/
>> +struct mov_to_cr {
>> +    uint8_t enabled;
>> +    uint8_t sync;
>> +    uint8_t onchangeonly;
>> +};
>> +
>> +struct mov_to_msr {
>> +    uint8_t enabled;
>> +    uint8_t extended_capture;
>> +};
>> +
>> +struct debug_event {
>> +    uint8_t enabled;
>> +};
>>> These are all internal structures - is there anything wrong with using
>>> bitfields here?
>> The use if bitfields is not good performance-wise AFAIK. Would there
>> be any benefit that would offset that?
>
> struct vcpu lives in a 4k page.  We avoid needlessly bloating it.
>
> However bitfields will not work with my suggestion as you cannot
> construct a pointer to 'enabled' if enabled is a bit.
>
> ~Andrew

That too.. I would rather keep these as bool_t's if possible.

Thanks,
Tamas

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