| Message ID | 20200911170738.82818-4-leobras.c@gmail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | DDW Indirect Mapping | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (4b552a4cbf286ff9dcdab19153f3c1c7d1680fab) |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 42 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
On 12/09/2020 03:07, Leonardo Bras wrote: > Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, > > Currently both iommu_alloc_coherent() and iommu_free_coherent() align the > desired allocation size to PAGE_SIZE, and gets system pages and IOMMU > mappings (TCEs) for that value. > > When IOMMU_PAGE_SIZE < PAGE_SIZE, this behavior may cause unnecessary > TCEs to be created for mapping the whole system page. > > Example: > - PAGE_SIZE = 64k, IOMMU_PAGE_SIZE() = 4k > - iommu_alloc_coherent() is called for 128 bytes > - 1 system page (64k) is allocated > - 16 IOMMU pages (16 x 4k) are allocated (16 TCEs used) > > It would be enough to use a single TCE for this, so 15 TCEs are > wasted in the process. > > Update iommu_*_coherent() to make sure the size alignment happens only > for IOMMU_PAGE_SIZE() before calling iommu_alloc() and iommu_free(). > > Also, on iommu_range_alloc(), replace ALIGN(n, 1 << tbl->it_page_shift) > with IOMMU_PAGE_ALIGN(n, tbl), which is easier to read and does the > same. This seems alright but rather unrelated to the series, probably makes sense to post it separately. Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru> > > Signed-off-by: Leonardo Bras <leobras.c@gmail.com> > --- > arch/powerpc/kernel/iommu.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c > index 9704f3f76e63..7961645a6980 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); > 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) { > @@ -900,10 +901,9 @@ 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); > size = PAGE_ALIGN(size); > free_pages((unsigned long)vaddr, get_order(size)); >
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c index 9704f3f76e63..7961645a6980 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); 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) { @@ -900,10 +901,9 @@ 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); size = PAGE_ALIGN(size); free_pages((unsigned long)vaddr, get_order(size));
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Currently both iommu_alloc_coherent() and iommu_free_coherent() align the desired allocation size to PAGE_SIZE, and gets system pages and IOMMU mappings (TCEs) for that value. When IOMMU_PAGE_SIZE < PAGE_SIZE, this behavior may cause unnecessary TCEs to be created for mapping the whole system page. Example: - PAGE_SIZE = 64k, IOMMU_PAGE_SIZE() = 4k - iommu_alloc_coherent() is called for 128 bytes - 1 system page (64k) is allocated - 16 IOMMU pages (16 x 4k) are allocated (16 TCEs used) It would be enough to use a single TCE for this, so 15 TCEs are wasted in the process. Update iommu_*_coherent() to make sure the size alignment happens only for IOMMU_PAGE_SIZE() before calling iommu_alloc() and iommu_free(). Also, on iommu_range_alloc(), replace ALIGN(n, 1 << tbl->it_page_shift) with IOMMU_PAGE_ALIGN(n, tbl), which is easier to read and does the same. Signed-off-by: Leonardo Bras <leobras.c@gmail.com> --- arch/powerpc/kernel/iommu.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)