Re: [PATCH for-4.19???] x86/physdev: replace physdev_{,un}map_pirq() checking against DOMID_SELF

[Jan Beulich <jbeulich@suse.com>]

On 12.06.2024 12:52, Roger Pau Monné wrote:
> On Wed, Jun 12, 2024 at 10:44:56AM +0200, Jan Beulich wrote:
>> It's hardly ever correct to check for just DOMID_SELF, as guests have
>> ways to figure out their domain IDs and hence could instead use those as
>> inputs to respective hypercalls. Note, however, that for ordinary DomU-s
>> the adjustment is relaxing things rather than tightening them, since
>> - as a result of XSA-237 - the respective XSM checks would have rejected
>> self (un)mapping attempts for other than the control domain.
>>
>> Since in physdev_map_pirq() handling overall is a little easier this
>> way, move obtaining of the domain pointer into the caller. Doing the
>> same for physdev_unmap_pirq() is just to keep both consistent in this
>> regard. For both this has the advantage that it is now provable (by the
>> build not failing) that there are no DOMID_SELF checks left (and none
>> could easily be re-added).
>>
>> Fixes: 0b469cd68708 ("Interrupt remapping to PIRQs in HVM guests")
>> Fixes: 9e1a3415b773 ("x86: fixes after emuirq changes")
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> 
> Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks.

> I wonder if we should introduce a helper to check for the current
> domain:
> 
> #define is_current_domain(d) ((d) == current->domain)

Hmm, that's not even shorter, and imo not any more "meaningful". Plus
it wouldn't cover the case where we have currd already in a local var.

Jan