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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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

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