Re: [PATCH 6/7] xen: Allow hardare domain != dom0

[Daniel De Graaf <dgdegra@tycho.nsa.gov>]

On 04/14/2014 03:56 AM, Jan Beulich wrote:
>>>> On 11.04.14 at 20:22, <dgdegra@tycho.nsa.gov> wrote:
>> On 04/11/2014 11:20 AM, Jan Beulich wrote:
>>>>>> On 11.04.14 at 17:07, <dgdegra@tycho.nsa.gov> wrote:
>>>> On 04/11/2014 05:13 AM, Jan Beulich wrote:
>>>> Otherwise, I think the is_hardware_domain definition should be:
>>>>
>>>> #ifdef CONFIG_LATE_HWDOM
>>>> #define is_hardware_domain(_d) ((_d)->domain_id == hardware_domid)
>>>> #else
>>>> #define is_hardware_domain(_d) ((_d)->domain_id == 0)
>>>> #endif
>>>>
>>>> This also allows hardware_domid to be declared inside the #ifdef.
>>>
>>> But that still wouldn't necessarily do the correct thing for any use of
>>> the macro before that new special case code in domain_create() got
>>> run. Maybe my thinking of this is wrong, but as I tried to state above,
>>> I would expect Dom0 to be the hardware domain up to the point
>>> where the intended hardware domain gets created, at which point all
>>> state Dom0 obtained because of having been the de-facto hardware
>>> domain get transferred to hardware_domain.
>>
>> I agree with this in most cases, and I think the few places where that
>> is not true should be changed to make them more explicit.  This must
>> include all checks in domain_create and those in functions called from
>> domain_create, because (d == hardware_domain) is always false inside
>> domain_create.  An initial version of this patch is below, but unless
>> there are objections I plan to integrate it into patch 1 to avoid doing
>> (d->domain_id == 0) => is_hardware_domain => is_hardware_domain_by_id
>> for the ARM code.
>
> Integration into any earlier patch would work only if we reverted
> what was already applied.

Ah, I didn't see that part of the series was applied.  Anyway, I didn't
really like how far the full version (larger than the RFC below) ended up
having to propagate the _by_id version, so a different solution would be
better.

>> ------------------------------>8------------------------
>>
>> Subject: [PATCH RFC 6/8] xen: introduce is_hardware_domain_by_id
>
> Certainly not very nice a name, and also not very nice to then have
> two ways to check, which likely people will not always distinguish
> properly. I think this needs some better idea, albeit I can't immediately
> offer one.
>
> Jan

If the assignment to hardware_domain is moved into domain_create, this
makes the (d == hardware_domain) version of is_hardware_domain work as
expected, and removes the need for is_hardware_domain_by_id.  This also
makes the initialization look a bit cleaner; the patch will be posted
momentarily.

-- 
Daniel De Graaf
National Security Agency