Re: [Xen-devel] [PATCH v3 3/3] x86/hvm: Use white-lists for HVM param guest accessibility checks

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.05.15 at 16:43, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 05/05/15 15:29, Jan Beulich wrote:
>>>>> On 05.05.15 at 16:09, <Paul.Durrant@xxxxxxxxxx> wrote:
>>>> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
>>>> Sent: 05 May 2015 11:54
>>>> On 05/05/15 11:25, Paul Durrant wrote:
>>>>> @@ -5657,21 +5664,11 @@ static int hvm_allow_set_param(struct domain
>>>> *d,
>>>>>      case HVM_PARAM_IDENT_PT:
>>>>>      case HVM_PARAM_DM_DOMAIN:
>>>>>      case HVM_PARAM_ACPI_S_STATE:
>>>> I think you can safely elide the above cases into default.  All that
>>>> matters in this case is that none of the whitelisted parameters need to
>>>> pause the domain.
>>>>
>>> I think you and Jan differ there, unless I misunderstood Jan.
>> Right, I specifically asked for these to be retained. It's just that
>> the comment preceding them is not visible from the patch
>> context, so that purpose isn't obvious here.
> 
> I would question its usefulness as documentation, given that its
> position in the code is now removed from the actual implementation.

Leaving aside the fact that these perhaps all shouldn't be used
by the guest anyway - if the implementation changed to no
longer require pausing of the domain, the argument for excluding
them from the white list would vanish, and hence they could
become guest accessible if so desired. And the code now being
far away from the actual implementation may even be considered
an extra argument for stating explicitly what would otherwise
possibly be quite obvious.

Jan


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