On Sat, 2020-08-22 at 20:07 +1000, Alexey Kardashevskiy wrote: > > On 18/08/2020 09:40, Leonardo Bras wrote: > > Both iommu_alloc_coherent() and iommu_free_coherent() assume that once > > size is aligned to PAGE_SIZE it will be aligned to IOMMU_PAGE_SIZE. > > The only case when it is not aligned is when IOMMU_PAGE_SIZE > PAGE_SIZE > which is unlikely but not impossible, we could configure the kernel for > 4K system pages and 64K IOMMU pages I suppose. Do we really want to do > this here, or simply put WARN_ON(tbl->it_page_shift > PAGE_SHIFT)?
I think it would be better to keep the code as much generic as possible regarding page sizes. > Because if we want the former (==support), then we'll have to align the > size up to the bigger page size when allocating/zeroing system pages, > etc. This part I don't understand. Why do we need to align everything to the bigger pagesize? I mean, is not that enough that the range [ret, ret + size[ is both allocated by mm and mapped on a iommu range? Suppose a iommu_alloc_coherent() of 16kB on PAGESIZE = 4k and IOMMU_PAGE_SIZE() == 64k. Why 4 * cpu_pages mapped by a 64k IOMMU page is not enough? All the space the user asked for is allocated and mapped for DMA. > Bigger pages are not the case here as I understand it. I did not get this part, what do you mean? > > Update those functions to guarantee alignment with requested size > > using IOMMU_PAGE_ALIGN() before doing iommu_alloc() / iommu_free(). > > > > Also, on iommu_range_alloc(), replace ALIGN(n, 1 << tbl->it_page_shift) > > with IOMMU_PAGE_ALIGN(n, tbl), which seems easier to read. > > > > Signed-off-by: Leonardo Bras <leobra...@gmail.com> > > --- > > arch/powerpc/kernel/iommu.c | 17 +++++++++-------- > > 1 file changed, 9 insertions(+), 8 deletions(-) > > > > diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c > > index 9704f3f76e63..d7086087830f 100644 > > --- a/arch/powerpc/kernel/iommu.c > > +++ b/arch/powerpc/kernel/iommu.c > > @@ -237,10 +237,9 @@ static unsigned long iommu_range_alloc(struct device > > *dev, > > } > > > > if (dev) > > - boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1, > > - 1 << tbl->it_page_shift); > > + boundary_size = IOMMU_PAGE_ALIGN(dma_get_seg_boundary(dev) + 1, > > tbl); > > Run checkpatch.pl, should complain about a long line. It's 86 columns long, which is less than the new limit of 100 columns Linus announced a few weeks ago. checkpatch.pl was updated too: https://www.phoronix.com/scan.php?page=news_item&px=Linux-Kernel-Deprecates-80-Col > > > > else > > - boundary_size = ALIGN(1UL << 32, 1 << tbl->it_page_shift); > > + boundary_size = IOMMU_PAGE_ALIGN(1UL << 32, tbl); > > /* 4GB boundary for iseries_hv_alloc and iseries_hv_map */ > > > > n = iommu_area_alloc(tbl->it_map, limit, start, npages, tbl->it_offset, > > @@ -858,6 +857,7 @@ void *iommu_alloc_coherent(struct device *dev, struct > > iommu_table *tbl, > > unsigned int order; > > unsigned int nio_pages, io_order; > > struct page *page; > > + size_t size_io = size; > > > > size = PAGE_ALIGN(size); > > order = get_order(size); > > @@ -884,8 +884,9 @@ void *iommu_alloc_coherent(struct device *dev, struct > > iommu_table *tbl, > > memset(ret, 0, size); > > > > /* Set up tces to cover the allocated range */ > > - nio_pages = size >> tbl->it_page_shift; > > - io_order = get_iommu_order(size, tbl); > > + size_io = IOMMU_PAGE_ALIGN(size_io, tbl); > > + nio_pages = size_io >> tbl->it_page_shift; > > + io_order = get_iommu_order(size_io, tbl); > > mapping = iommu_alloc(dev, tbl, ret, nio_pages, DMA_BIDIRECTIONAL, > > mask >> tbl->it_page_shift, io_order, 0); > > if (mapping == DMA_MAPPING_ERROR) { > > @@ -900,11 +901,11 @@ void iommu_free_coherent(struct iommu_table *tbl, > > size_t size, > > void *vaddr, dma_addr_t dma_handle) > > { > > if (tbl) { > > - unsigned int nio_pages; > > + size_t size_io = IOMMU_PAGE_ALIGN(size, tbl); > > + unsigned int nio_pages = size_io >> tbl->it_page_shift; > > > > - size = PAGE_ALIGN(size); > > - nio_pages = size >> tbl->it_page_shift; > > iommu_free(tbl, dma_handle, nio_pages); > > + > > Unrelated new line. Will be removed. Thanks! > > > > size = PAGE_ALIGN(size); > > free_pages((unsigned long)vaddr, get_order(size)); > > } > >
