On Fri, 18 Mar 2022 14:27:32 -0300
Jason Gunthorpe <[email protected]> wrote:
> +/*
> + * The area takes a slice of the pages from start_bytes to start_byte +
> length
> + */
> +static struct iopt_area *
> +iopt_alloc_area(struct io_pagetable *iopt, struct iopt_pages *pages,
> + unsigned long iova, unsigned long start_byte,
> + unsigned long length, int iommu_prot, unsigned int flags)
> +{
> + struct iopt_area *area;
> + int rc;
> +
> + area = kzalloc(sizeof(*area), GFP_KERNEL);
> + if (!area)
> + return ERR_PTR(-ENOMEM);
> +
> + area->iopt = iopt;
> + area->iommu_prot = iommu_prot;
> + area->page_offset = start_byte % PAGE_SIZE;
> + area->pages_node.start = start_byte / PAGE_SIZE;
> + if (check_add_overflow(start_byte, length - 1, &area->pages_node.last))
> + return ERR_PTR(-EOVERFLOW);
> + area->pages_node.last = area->pages_node.last / PAGE_SIZE;
> + if (WARN_ON(area->pages_node.last >= pages->npages))
> + return ERR_PTR(-EOVERFLOW);
@area leaked in the above two error cases.
> +
> + down_write(&iopt->iova_rwsem);
> + if (flags & IOPT_ALLOC_IOVA) {
> + rc = iopt_alloc_iova(iopt, &iova,
> + (uintptr_t)pages->uptr + start_byte,
> + length);
> + if (rc)
> + goto out_unlock;
> + }
> +
> + if (check_add_overflow(iova, length - 1, &area->node.last)) {
> + rc = -EOVERFLOW;
> + goto out_unlock;
> + }
> +
> + if (!(flags & IOPT_ALLOC_IOVA)) {
> + if ((iova & (iopt->iova_alignment - 1)) ||
> + (length & (iopt->iova_alignment - 1)) || !length) {
> + rc = -EINVAL;
> + goto out_unlock;
> + }
> +
> + /* No reserved IOVA intersects the range */
> + if (interval_tree_iter_first(&iopt->reserved_iova_itree, iova,
> + area->node.last)) {
> + rc = -ENOENT;
> + goto out_unlock;
> + }
> +
> + /* Check that there is not already a mapping in the range */
> + if (iopt_area_iter_first(iopt, iova, area->node.last)) {
> + rc = -EADDRINUSE;
> + goto out_unlock;
> + }
> + }
> +
> + /*
> + * The area is inserted with a NULL pages indicating it is not fully
> + * initialized yet.
> + */
> + area->node.start = iova;
> + interval_tree_insert(&area->node, &area->iopt->area_itree);
> + up_write(&iopt->iova_rwsem);
> + return area;
> +
> +out_unlock:
> + up_write(&iopt->iova_rwsem);
> + kfree(area);
> + return ERR_PTR(rc);
> +}
...
> +/**
> + * iopt_access_pages() - Return a list of pages under the iova
> + * @iopt: io_pagetable to act on
> + * @iova: Starting IOVA
> + * @length: Number of bytes to access
> + * @out_pages: Output page list
> + * @write: True if access is for writing
> + *
> + * Reads @npages starting at iova and returns the struct page * pointers.
> These
> + * can be kmap'd by the caller for CPU access.
> + *
> + * The caller must perform iopt_unaccess_pages() when done to balance this.
> + *
> + * iova can be unaligned from PAGE_SIZE. The first returned byte starts at
> + * page_to_phys(out_pages[0]) + (iova % PAGE_SIZE). The caller promises not
> to
> + * touch memory outside the requested iova slice.
> + *
> + * FIXME: callers that need a DMA mapping via a sgl should create another
> + * interface to build the SGL efficiently
> + */
> +int iopt_access_pages(struct io_pagetable *iopt, unsigned long iova,
> + unsigned long length, struct page **out_pages, bool write)
> +{
> + unsigned long cur_iova = iova;
> + unsigned long last_iova;
> + struct iopt_area *area;
> + int rc;
> +
> + if (!length)
> + return -EINVAL;
> + if (check_add_overflow(iova, length - 1, &last_iova))
> + return -EOVERFLOW;
> +
> + down_read(&iopt->iova_rwsem);
> + for (area = iopt_area_iter_first(iopt, iova, last_iova); area;
> + area = iopt_area_iter_next(area, iova, last_iova)) {
> + unsigned long last = min(last_iova, iopt_area_last_iova(area));
> + unsigned long last_index;
> + unsigned long index;
> +
> + /* Need contiguous areas in the access */
> + if (iopt_area_iova(area) < cur_iova || !area->pages) {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Should this be (cur_iova != iova && iopt_area_iova(area) < cur_iova)?
I can't see how we'd require in-kernel page users to know the iopt_area
alignment from userspace, so I think this needs to skip the first
iteration. Thanks,
Alex
> + rc = -EINVAL;
> + goto out_remove;
> + }
> +
> + index = iopt_area_iova_to_index(area, cur_iova);
> + last_index = iopt_area_iova_to_index(area, last);
> + rc = iopt_pages_add_user(area->pages, index, last_index,
> + out_pages, write);
> + if (rc)
> + goto out_remove;
> + if (last == last_iova)
> + break;
> + /*
> + * Can't cross areas that are not aligned to the system page
> + * size with this API.
> + */
> + if (cur_iova % PAGE_SIZE) {
> + rc = -EINVAL;
> + goto out_remove;
> + }
> + cur_iova = last + 1;
> + out_pages += last_index - index;
> + atomic_inc(&area->num_users);
> + }
> +
> + up_read(&iopt->iova_rwsem);
> + return 0;
> +
> +out_remove:
> + if (cur_iova != iova)
> + iopt_unaccess_pages(iopt, iova, cur_iova - iova);
> + up_read(&iopt->iova_rwsem);
> + return rc;
> +}
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