On Thu, May 19, 2022 at 02:12:04PM +0200, Jan Beulich wrote:
> On 06.05.2022 13:16, Roger Pau Monné wrote:
> > On Mon, Apr 25, 2022 at 10:40:55AM +0200, Jan Beulich wrote:
> >> ---
> >> An alternative to the ASSERT()s added to set_iommu_ptes_present() would
> >> be to make the function less general-purpose; it's used in a single
> >> place only after all (i.e. it might as well be folded into its only
> >> caller).
> >
> > I would think adding a comment that the function requires the PDE to
> > be empty would be good.
>
> But that's not the case - what the function expects to be clear is
> what is being ASSERT()ed.
>
> > Also given the current usage we could drop
> > the nr_ptes parameter and just name the function fill_pde() or
> > similar.
>
> Right, but that would want to be a separate change.
>
> >> --- a/xen/drivers/passthrough/amd/iommu_map.c
> >> +++ b/xen/drivers/passthrough/amd/iommu_map.c
> >> @@ -115,7 +115,19 @@ static void set_iommu_ptes_present(unsig
> >>
> >> while ( nr_ptes-- )
> >> {
> >> - set_iommu_pde_present(pde, next_mfn, 0, iw, ir);
> >> + ASSERT(!pde->next_level);
> >> + ASSERT(!pde->u);
> >> +
> >> + if ( pde > table )
> >> + ASSERT(pde->ign0 == find_first_set_bit(pde - table));
> >> + else
> >> + ASSERT(pde->ign0 == PAGE_SHIFT - 3);
> >
> > I think PAGETABLE_ORDER would be clearer here.
>
> I disagree - PAGETABLE_ORDER is a CPU-side concept. It's not used anywhere
> in IOMMU code afaics.
Isn't PAGE_SHIFT also a CPU-side concept in the same way? I'm not
sure what's the rule for declaring that PAGE_SHIFT is fine to use in
IOMMU code but not PAGETABLE_ORDER.
Thanks, Roger.
