Re: [PATCH v2 6/8] iommu: Move IOMMU pagesize check to attach_device

[Robin Murphy]

On 2021-09-01 18:14, Sven Peter wrote:
> On Tue, Aug 31, 2021, at 23:39, Alyssa Rosenzweig wrote:
> > > +	if ((1 << __ffs(domain->pgsize_bitmap)) > PAGE_SIZE) {
> >
> > Not a fan of this construction. Could you assign `(1 <<
> > __ffs(domain->pgsize_bitmap))` to an appropriately named temporary (e.g
> > min_io_pgsize) so it's clearer what's going on?
>
> Good point, will do that for the next version.

Or maybe just test "__ffs(domain->pgsize_bitmap) > PAGE_SHIFT", or 
perhaps even avoid shifts altogether with something like 
"domain->pgsize_bitmap & (PAGE_SIZE | PAGE_SIZE - 1)".

Robin.

> > > +		pr_warn("IOMMU page size cannot represent CPU pages.\n");
> >
> > "Represent" how?
>
> Looks like I dropped an "exactly" there when taking this line from iova.c :)
>
>
>
> Thanks,
>
>
> Sven