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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

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@xxxxxxxx>

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

I wonder if we should introduce a helper to check for the current
domain:

#define is_current_domain(d) ((d) == current->domain)

Or similar.

Thanks, Roger.