On Tue, Oct 11, 2011 at 7:49 AM, Ohad Ben-Cohen [off-list ref] wrote:

?int iommu_map(struct iommu_domain *domain, unsigned long iova,
- ? ? ? ? ? ? phys_addr_t paddr, int gfp_order, int prot)
+ ? ? ? ? ? ? phys_addr_t paddr, int size, int prot)
?{

Even though it is not realistic that size becomes larger than 1 <<
((sizeof(int) * 8) - 1),
I think the type of size should be size_t.

- ? ? ? size_t size;
+ ? ? ? unsigned long orig_iova = iova;
+ ? ? ? int ret = 0, orig_size = size;

? ? ? ?if (unlikely(domain->ops->map == NULL))
? ? ? ? ? ? ? ?return -ENODEV;

- ? ? ? size ? ? ? ? = PAGE_SIZE << gfp_order;
+ ? ? ? /*
+ ? ? ? ?* both the virtual address and the physical one, as well as
+ ? ? ? ?* the size of the mapping, must be aligned (at least) to the
+ ? ? ? ?* size of the smallest page supported by the hardware
+ ? ? ? ?*/
+ ? ? ? if (!IS_ALIGNED(iova | paddr | size, domain->ops->min_pagesz)) {
+ ? ? ? ? ? ? ? pr_err("unaligned: iova 0x%lx pa 0x%lx size 0x%x min_pagesz "
+ ? ? ? ? ? ? ? ? ? ? ? "0x%x\n", iova, (unsigned long)paddr,
+ ? ? ? ? ? ? ? ? ? ? ? size, domain->ops->min_pagesz);
+ ? ? ? ? ? ? ? return -EINVAL;
+ ? ? ? }
+
+ ? ? ? pr_debug("map: iova 0x%lx pa 0x%lx size 0x%x\n", iova,
+ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? (unsigned long)paddr, size);
+
+ ? ? ? while (size) {
+ ? ? ? ? ? ? ? unsigned long pgsize, addr_merge = iova | paddr;
+ ? ? ? ? ? ? ? unsigned int pgsize_idx;
+
+ ? ? ? ? ? ? ? /* Max page size that still fits into 'size' */
+ ? ? ? ? ? ? ? pgsize_idx = __fls(size);
+
+ ? ? ? ? ? ? ? /* need to consider alignment requirements ? */
+ ? ? ? ? ? ? ? if (likely(addr_merge)) {
+ ? ? ? ? ? ? ? ? ? ? ? /* Max page size allowed by both iova and paddr */
+ ? ? ? ? ? ? ? ? ? ? ? unsigned int align_pgsize_idx = __ffs(addr_merge);
+
+ ? ? ? ? ? ? ? ? ? ? ? pgsize_idx = min(pgsize_idx, align_pgsize_idx);
+ ? ? ? ? ? ? ? }
+
+ ? ? ? ? ? ? ? /* build a mask of acceptable page sizes */
+ ? ? ? ? ? ? ? pgsize = (1UL << (pgsize_idx + 1)) - 1;
+
+ ? ? ? ? ? ? ? /* throw away page sizes not supported by the hardware */
+ ? ? ? ? ? ? ? pgsize &= domain->ops->pgsize_bitmap;
+
+ ? ? ? ? ? ? ? /* make sure we're still sane */
+ ? ? ? ? ? ? ? BUG_ON(!pgsize);

- ? ? ? BUG_ON(!IS_ALIGNED(iova | paddr, size));
+ ? ? ? ? ? ? ? /* pick the biggest page */
+ ? ? ? ? ? ? ? pgsize_idx = __fls(pgsize);
+ ? ? ? ? ? ? ? pgsize = 1UL << pgsize_idx;

- ? ? ? return domain->ops->map(domain, iova, paddr, gfp_order, prot);
+ ? ? ? ? ? ? ? /* convert index to page order */
+ ? ? ? ? ? ? ? pgsize_idx -= PAGE_SHIFT;
+
+ ? ? ? ? ? ? ? pr_debug("mapping: iova 0x%lx pa 0x%lx order %u\n", iova,
+ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? (unsigned long)paddr, pgsize_idx);
+
+ ? ? ? ? ? ? ? ret = domain->ops->map(domain, iova, paddr, pgsize_idx, prot);
+ ? ? ? ? ? ? ? if (ret)
+ ? ? ? ? ? ? ? ? ? ? ? break;
+
+ ? ? ? ? ? ? ? iova += pgsize;
+ ? ? ? ? ? ? ? paddr += pgsize;
+ ? ? ? ? ? ? ? size -= pgsize;
+ ? ? ? }
+
+ ? ? ? /* unroll mapping in case something went wrong */
+ ? ? ? if (ret)
+ ? ? ? ? ? ? ? iommu_unmap(domain, orig_iova, orig_size);
+

domain->ops->map() might return error because a mapping already exists
in the range from iova until iova + size.
Thus, it should be
iommu_unmap(domain, orig_iova, orig_size - size)

Regards,

KyongHo