Hi Shameer, On 8/1/19 3:46 PM, Shameerali Kolothum Thodi wrote: > Hi Eric, > >> -----Original Message----- >> From: Eric Auger [mailto:[email protected]] >> Sent: 30 July 2019 15:01 >> To: [email protected]; [email protected]; [email protected]; >> [email protected]; [email protected]; >> [email protected]; [email protected]; >> [email protected]; [email protected] >> Cc: Shameerali Kolothum Thodi <[email protected]> >> 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. >> >> 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. > > I had a quick run with this patch on one of our boards(D05) where we > actually have an untranslated HW MSI region. > > Before.. > estuary:/$ cat /sys/kernel/iommu_groups/3/reserved_regions > 0x0000000008000000 0x00000000080fffff msi > 0x00000000c6010000 0x00000000c601ffff msi > > After... > estuary:/$ cat /sys/kernel/iommu_groups/3/reserved_regions > 0x00000000c6010000 0x00000000c601ffff msi > 0x0000000008000000 0x00000000080fffff msi > > I think the order is reversed now because they are both different types, but > are > called "msi". Slightly confusing, but not sure it's a good idea to change the > description to something more obvious.
Thank you very much for the testing. I have been working on another version which removes the recursiveness but still sorts by start address and then by type. I prefer this new one as this shouldn't change the order. I will submit it asap. Thanks Eric > > Cheers, > Shameer > >> Signed-off-by: Eric Auger <[email protected]> >> >> --- >> --- >> 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 >
