Re: [PATCH v16 4/5] xen/arm: translate virtual PCI bus topology for guests

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

On Fri, May 24, 2024 at 02:21:09PM +0100, Julien Grall wrote:
> Hi,
> 
> Sorry I didn't notice there was a v16 and posted comments on the v15. The
> only one is about the size of the list we iterate.
> 
> On 23/05/2024 08:48, Roger Pau Monné wrote:
> > On Wed, May 22, 2024 at 06:59:23PM -0400, Stewart Hildebrand wrote:
> > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > > +    }
> > > -    return sbdf;
> > > +    return translated;
> > >   }
> > >   static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
> > >                             register_t *r, void *p)
> > >   {
> > >       struct pci_host_bridge *bridge = p;
> > > -    pci_sbdf_t sbdf = vpci_sbdf_from_gpa(bridge, info->gpa);
> > > +    pci_sbdf_t sbdf;
> > >       const unsigned int access_size = (1U << info->dabt.size) * 8;
> > >       const register_t invalid = GENMASK_ULL(access_size - 1, 0);
> > 
> > Do you know why the invalid value is truncated to the access size.
> 
> Because no other callers are doing the truncation and therefore the guest
> would read 1s even for 8-byte unsigned access.

I think forcing all handlers to do the truncation is a lot of
duplication, and more risky than just doing it in the dispatcher
itself (handle_read()), see my reply to 1/5.

Thanks, Roger.