Messages in this thread Patch in this message | | | From | Eric Auger <> | Subject | [PATCH] iommu: revisit iommu_insert_resv_region() implementation | Date | Tue, 30 Jul 2019 16:00:55 +0200 |
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Current implementation is recursive and in case of allocation failure the existing @regions list is altered. A non recursive version looks better for maintainability and simplifies the error handling. We use a separate stack for overlapping segment merging.
Note this new implementation may change the region order of appearance in /sys/kernel/iommu_groups/<n>/reserved_regions files but this order has never been documented, see commit bc7d12b91bd3 ("iommu: Implement reserved_regions iommu-group sysfs file"). Previously the regions were sorted by start address. Now they are first sorted by type and within a type they are sorted by start address.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
--- --- drivers/iommu/iommu.c | 96 ++++++++++++++++++++++--------------------- 1 file changed, 50 insertions(+), 46 deletions(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 0c674d80c37f..7479f3d38e61 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -229,60 +229,64 @@ static ssize_t iommu_group_show_name(struct iommu_group *group, char *buf) * @new: new region to insert * @regions: list of regions * - * The new element is sorted by address with respect to the other - * regions of the same type. In case it overlaps with another - * region of the same type, regions are merged. In case it - * overlaps with another region of different type, regions are - * not merged. + * Elements are sorted by region type and elements of the same + * type are sorted by start address. Overlapping segments of the + * same type are merged. */ static int iommu_insert_resv_region(struct iommu_resv_region *new, struct list_head *regions) { - struct iommu_resv_region *region; - phys_addr_t start = new->start; - phys_addr_t end = new->start + new->length - 1; - struct list_head *pos = regions->next; + struct iommu_resv_region *iter, *tmp, *nr, *top; + struct list_head low, high, stack; + bool added = false; - while (pos != regions) { - struct iommu_resv_region *entry = - list_entry(pos, struct iommu_resv_region, list); - phys_addr_t a = entry->start; - phys_addr_t b = entry->start + entry->length - 1; - int type = entry->type; + INIT_LIST_HEAD(&low); + INIT_LIST_HEAD(&high); + INIT_LIST_HEAD(&stack); - if (end < a) { - goto insert; - } else if (start > b) { - pos = pos->next; - } else if ((start >= a) && (end <= b)) { - if (new->type == type) - return 0; - else - pos = pos->next; - } else { - if (new->type == type) { - phys_addr_t new_start = min(a, start); - phys_addr_t new_end = max(b, end); - int ret; - - list_del(&entry->list); - entry->start = new_start; - entry->length = new_end - new_start + 1; - ret = iommu_insert_resv_region(entry, regions); - kfree(entry); - return ret; - } else { - pos = pos->next; - } - } - } -insert: - region = iommu_alloc_resv_region(new->start, new->length, - new->prot, new->type); - if (!region) + nr = iommu_alloc_resv_region(new->start, new->length, + new->prot, new->type); + if (!nr) return -ENOMEM; - list_add_tail(®ion->list, pos); + /* + * Elements are dispatched into 3 lists: low/high contain + * segments of lower/higher types than @new; only segments + * with same type as @new remain in @regions, including @new + * ordered inserted by start address + */ + list_for_each_entry_safe(iter, tmp, regions, list) { + if (iter->type < nr->type) { + list_move_tail(&iter->list, &low); + } else if (iter->type > nr->type) { + list_move_tail(&iter->list, &high); + } else if (nr->start <= iter->start && !added) { + list_add_tail(&nr->list, &iter->list); + added = true; + } + } + if (!added) + list_add_tail(&nr->list, regions); + + /* Merge overlapping segments in @regions, if any */ + list_move(regions->next, &stack); /* move the 1st elt to the stack */ + list_for_each_entry_safe(iter, tmp, regions, list) { + phys_addr_t top_end, iter_end = iter->start + iter->length - 1; + + top = list_last_entry(&stack, struct iommu_resv_region, list); + top_end = top->start + top->length - 1; + + if (iter->start > top_end + 1) { + list_move(&iter->list, &top->list); + } else { + top->length = max(top_end, iter_end) - top->start + 1; + list_del(&iter->list); + kfree(iter); + } + } + list_splice(&stack, regions); + list_splice(&low, regions); + list_splice_tail(&high, regions); return 0; } -- 2.20.1
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