On Wed, Mar 12, 2025 at 12:59:00PM +0000, Mostafa Saleh wrote:
> > --- a/drivers/iommu/io-pgtable-arm.c
> > +++ b/drivers/iommu/io-pgtable-arm.c
> > @@ -263,14 +263,13 @@ static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
> > void *cookie)
> > {
> > struct device *dev = cfg->iommu_dev;
> > - int order = get_order(size);
> > dma_addr_t dma;
> > void *pages;
> >
> > if (cfg->alloc)
> > pages = cfg->alloc(cookie, size, gfp);
> > else
> > - pages = iommu_alloc_pages_node(dev_to_node(dev), gfp, order);
> > + pages = iommu_alloc_pages_node_sz(dev_to_node(dev), gfp, size);
>
> Although, the current implementation of iommu_alloc_pages_node_sz() would round
> the size to order, but this is not correct according to the API definition
> "The returned allocation is round_up_pow_two(size) big, and is physically aligned
> to its size."
Yes.. The current implementation is limited to full PAGE_SIZE only,
the documentation imagines a future where it is not. Drivers should
ideally not assume the PAGE_SIZE limit during this conversion.
> I'd say we can align the size or use min with 64 bytes before calling the
> function would be enough (or change the API to state that allocations
> are rounded to order)
OK, like this:
if (cfg->alloc) {
pages = cfg->alloc(cookie, size, gfp);
} else {
/*
* For very small starting-level translation tables the HW
* requires a minimum alignment of at least 64 to cover all
* cases.
*/
pages = iommu_alloc_pages_node_sz(dev_to_node(dev), gfp,
max(size, 64));
}
Thanks,
Jason
