On (04/03/15 07:54), Benjamin Herrenschmidt wrote:
> > + limit = pool->end;
> > +
> > + /* The case below can happen if we have a small segment appended
> > + * to a large, or when the previous alloc was at the very end of
> > + * the available space. If so, go back to the beginning and flush.
> > + */
> > + if (start >= limit) {
> > + start = pool->start;
> > + if (!large_pool && iommu->lazy_flush != NULL)
> > + iommu->lazy_flush(iommu);
>
> Add need_flush = false;
A few clarifications, while I parse the rest of your comments:
Not sure I follow- need_flush is initialized to true at the start of the function?
> I only just noticed too, you completely dropped the code to honor
> the dma mask. Why that ? Some devices rely on this.
so that's an interesting question: the existing iommu_range_alloc() in
arch/sparc/kernel/iommu.c does not use the mask at all. I based most of
the code on this (except for the lock fragmentation part).
I dont know if this is arch specific.
>
> > + if (dev)
> > + boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1,
> > + 1 << iommu->table_shift);
> > + else
> > + boundary_size = ALIGN(1UL << 32, 1 << iommu->table_shift);
> > +
> > + shift = iommu->table_map_base >> iommu->table_shift;
> > + boundary_size = boundary_size >> iommu->table_shift;
> > + /*
> > + * if the skip_span_boundary_check had been set during init, we set
> > + * things up so that iommu_is_span_boundary() merely checks if the
> > + * (index + npages) < num_tsb_entries
> > + */
> > + if ((iommu->flags & IOMMU_NO_SPAN_BOUND) != 0) {
> > + shift = 0;
> > + boundary_size = iommu->poolsize * iommu->nr_pools;
> > + }
> > + n = iommu_area_alloc(iommu->map, limit, start, npages, shift,
> > + boundary_size, 0);
>
> You have completely dropped the alignment support. This will break
> drivers. There are cases (especially with consistent allocations) where
Again, not sure I follow? are you referring to the IOMMU_NO_SPAN_BOUND case?
That's very specific to LDC (sparc ldoms virtualization infra). The default
is to not have IOMMU_NO_SPAN_BOUND set.
For the rest of the drivers, the code that sets up boundary_size aligns things
in the same way as the ppc code.
> the driver have alignment constraints on the address, those must be
> preserved.
>
--Sowmini
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