From 4dbd258ff63e0597ee8fb44d277c6c701f5019d9 Mon Sep 17 00:00:00 2001 From: Eric Auger Date: Wed, 21 Aug 2019 14:09:40 +0200 Subject: [PATCH] iommu: Revisit iommu_insert_resv_region() implementation 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. The elements are sorted by start address and then by type, if their start address match. Note this new implementation may change the region order of appearance in /sys/kernel/iommu_groups//reserved_regions files but this order has never been documented, see commit bc7d12b91bd3 ("iommu: Implement reserved_regions iommu-group sysfs file"). Signed-off-by: Eric Auger Reviewed-by: Christoph Hellwig Signed-off-by: Joerg Roedel --- drivers/iommu/iommu.c | 96 +++++++++++++++++++++++++-------------------------- 1 file changed, 47 insertions(+), 49 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 0f585b6..b698093 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -286,60 +286,58 @@ 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 start address and overlapping segments + * of the same type are merged. */ -static int iommu_insert_resv_region(struct iommu_resv_region *new, - struct list_head *regions) +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; - - 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; - - 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; + struct iommu_resv_region *iter, *tmp, *nr, *top; + LIST_HEAD(stack); + + nr = iommu_alloc_resv_region(new->start, new->length, + new->prot, new->type); + if (!nr) + return -ENOMEM; + + /* First add the new element based on start address sorting */ + list_for_each_entry(iter, regions, list) { + if (nr->start < iter->start || + (nr->start == iter->start && nr->type <= iter->type)) + break; + } + list_add_tail(&nr->list, &iter->list); + + /* Merge overlapping segments of type nr->type in @regions, if any */ + list_for_each_entry_safe(iter, tmp, regions, list) { + phys_addr_t top_end, iter_end = iter->start + iter->length - 1; + + /* no merge needed on elements of different types than @nr */ + if (iter->type != nr->type) { + list_move_tail(&iter->list, &stack); + continue; + } + + /* look for the last stack element of same type as @iter */ + list_for_each_entry_reverse(top, &stack, list) + if (top->type == iter->type) + goto check_overlap; + + list_move_tail(&iter->list, &stack); + continue; + +check_overlap: + top_end = top->start + top->length - 1; + + if (iter->start > top_end + 1) { + list_move_tail(&iter->list, &stack); } 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; - } + top->length = max(top_end, iter_end) - top->start + 1; + list_del(&iter->list); + kfree(iter); } } -insert: - region = iommu_alloc_resv_region(new->start, new->length, - new->prot, new->type); - if (!region) - return -ENOMEM; - - list_add_tail(®ion->list, pos); + list_splice(&stack, regions); return 0; } -- 2.7.4