Re: [Xen-devel] [v4][PATCH 04/19] xen/passthrough: extend hypercall to support rdm reservation policy

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.07.15 at 12:56, <tiejun.chen@xxxxxxxxx> wrote:
>>>> Yes, this demonstrates my point.  Each of these is a single-bit boolean
>>>> value that takes up a single bit -- either on or off.  But here you have
>>>> three values -- NO_DRM, RELAXED, and STRICT, that take up two bits.  If
>>>
>>> Is this fine to you?
>>>
>>> #define _XEN_DOMCTL_DEV_NO_RDM          0
>>> #define XEN_DOMCTL_DEV_NO_RDM           (1U<<_XEN_DOMCTL_DEV_NO_RDM)
>>> #define _XEN_DOMCTL_DEV_RDM_RELAXED     1
>>> #define XEN_DOMCTL_DEV_RDM_RELAXED      (1U<<_XEN_DOMCTL_DEV_RDM_RELAXED)
>>> #define _XEN_DOMCTL_DEV_RDM_STRICT      2
>>> #define XEN_DOMCTL_DEV_RDM_STRICT       (1U<<_XEN_DOMCTL_DEV_RDM_STRICT)
>>
>> AIUI these aren't individual flags, but kind of an enumeration. I.e.
>> you should keep the original definitions and add - as suggested by
>> George - a mask (two bits wide right now).
>>
> 
> Okay but George also thought NO_RDM may be pointless since we can just 
> ignore this flag field simply for DT device, and he also thought one bit 
> may be fine enough to cover two cases, strict and relaxed. So maybe 
> finally, here is,
> 
> #define XEN_DOMCTL_DEV_RDM_RELAXED    1
> #define XEN_DOMCTL_DEV_RDM_FLAGS_MASK (0x1)

Except that then you don't need a mask.

Jan


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