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iommu: Decouple iommu_map_sg from CPU page size

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If the IOMMU supports pages smaller than the CPU page size, segments
which lie at offsets within the CPU page may be mapped based on the
finer-grained IOMMU page boundaries. This minimises the amount of
non-buffer memory between the CPU page boundary and the start of the
segment which must be mapped and therefore exposed to the device, and
brings the default iommu_map_sg implementation in line with
iommu_map/unmap with respect to alignment.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2014-11-25 17:50:55 +00:00 committed by Joerg Roedel
parent 0690cbd2e5
commit 18f2340990
1 changed files with 15 additions and 5 deletions
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20
drivers/iommu/iommu.c
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@ -1143,14 +1143,24 @@ size_t default_iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
{
struct scatterlist *s;
size_t mapped = 0;
unsigned int i;
unsigned int i, min_pagesz;
int ret;
for_each_sg(sg, s, nents, i) {
phys_addr_t phys = page_to_phys(sg_page(s));
if (unlikely(domain->ops->pgsize_bitmap == 0UL))
return 0;
/* We are mapping on page boundarys, so offset must be 0 */
if (s->offset)
min_pagesz = 1 << __ffs(domain->ops->pgsize_bitmap);
for_each_sg(sg, s, nents, i) {
phys_addr_t phys = page_to_phys(sg_page(s)) + s->offset;
/*
* We are mapping on IOMMU page boundaries, so offset within
* the page must be 0. However, the IOMMU may support pages
* smaller than PAGE_SIZE, so s->offset may still represent
* an offset of that boundary within the CPU page.
*/
if (!IS_ALIGNED(s->offset, min_pagesz))
goto out_err;
ret = iommu_map(domain, iova + mapped, phys, s->length, prot);