static long vfio_unmap_unpin()

in vfio_iommu_type1.c [1076:1158]

• 56 lines of code
• 12 McCabe index (conditional complexity)

static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
			     bool do_accounting)
{
	dma_addr_t iova = dma->iova, end = dma->iova + dma->size;
	struct vfio_domain *domain, *d;
	LIST_HEAD(unmapped_region_list);
	struct iommu_iotlb_gather iotlb_gather;
	int unmapped_region_cnt = 0;
	long unlocked = 0;

	if (!dma->size)
		return 0;

	if (list_empty(&iommu->domain_list))
		return 0;

	/*
	 * We use the IOMMU to track the physical addresses, otherwise we'd
	 * need a much more complicated tracking system.  Unfortunately that
	 * means we need to use one of the iommu domains to figure out the
	 * pfns to unpin.  The rest need to be unmapped in advance so we have
	 * no iommu translations remaining when the pages are unpinned.
	 */
	domain = d = list_first_entry(&iommu->domain_list,
				      struct vfio_domain, next);

	list_for_each_entry_continue(d, &iommu->domain_list, next) {
		iommu_unmap(d->domain, dma->iova, dma->size);
		cond_resched();
	}

	iommu_iotlb_gather_init(&iotlb_gather);
	while (iova < end) {
		size_t unmapped, len;
		phys_addr_t phys, next;

		phys = iommu_iova_to_phys(domain->domain, iova);
		if (WARN_ON(!phys)) {
			iova += PAGE_SIZE;
			continue;
		}

		/*
		 * To optimize for fewer iommu_unmap() calls, each of which
		 * may require hardware cache flushing, try to find the
		 * largest contiguous physical memory chunk to unmap.
		 */
		for (len = PAGE_SIZE;
		     !domain->fgsp && iova + len < end; len += PAGE_SIZE) {
			next = iommu_iova_to_phys(domain->domain, iova + len);
			if (next != phys + len)
				break;
		}

		/*
		 * First, try to use fast unmap/unpin. In case of failure,
		 * switch to slow unmap/unpin path.
		 */
		unmapped = unmap_unpin_fast(domain, dma, &iova, len, phys,
					    &unlocked, &unmapped_region_list,
					    &unmapped_region_cnt,
					    &iotlb_gather);
		if (!unmapped) {
			unmapped = unmap_unpin_slow(domain, dma, &iova, len,
						    phys, &unlocked);
			if (WARN_ON(!unmapped))
				break;
		}
	}

	dma->iommu_mapped = false;

	if (unmapped_region_cnt) {
		unlocked += vfio_sync_unpin(dma, domain, &unmapped_region_list,
					    &iotlb_gather);
	}

	if (do_accounting) {
		vfio_lock_acct(dma, -unlocked, true);
		return 0;
	}
	return unlocked;
}