Re: [PATCH v12.2 01/15] vpci: use per-domain PCI lock to protect vpci structure

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

On Tue, Jan 23, 2024 at 03:32:12PM +0100, Jan Beulich wrote:
> On 15.01.2024 20:43, Stewart Hildebrand wrote:
> > @@ -2888,6 +2888,8 @@ int allocate_and_map_msi_pirq(struct domain *d, int 
> > index, int *pirq_p,
> >  {
> >      int irq, pirq, ret;
> >  
> > +    ASSERT(pcidevs_locked() || rw_is_locked(&d->pci_lock));
> 
> If either lock is sufficient to hold here, ...
> 
> > --- a/xen/arch/x86/physdev.c
> > +++ b/xen/arch/x86/physdev.c
> > @@ -123,7 +123,9 @@ int physdev_map_pirq(domid_t domid, int type, int 
> > *index, int *pirq_p,
> >  
> >      case MAP_PIRQ_TYPE_MSI:
> >      case MAP_PIRQ_TYPE_MULTI_MSI:
> > +        pcidevs_lock();
> >          ret = allocate_and_map_msi_pirq(d, *index, pirq_p, type, msi);
> > +        pcidevs_unlock();
> >          break;
> 

IIRC (Stewart can further comment) this is done holding the pcidevs
lock to keep the path unmodified, as there's no need to hold the
per-domain rwlock.

Roger.