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* [PATCH v2 1/2] iommu/iova: Retry from last rb tree node if iova search fails
@ 2020-08-20 12:49 vjitta
  2020-08-20 12:49 ` [PATCH v2 2/2] iommu/iova: Free global iova rcache on iova alloc failure vjitta
                   ` (2 more replies)
  0 siblings, 3 replies; 10+ messages in thread
From: vjitta @ 2020-08-20 12:49 UTC (permalink / raw)
  To: joro, iommu, linux-kernel; +Cc: vjitta, robin.murphy, vinmenon, kernel-team

From: Vijayanand Jitta <vjitta@codeaurora.org>

When ever a new iova alloc request comes iova is always searched
from the cached node and the nodes which are previous to cached
node. So, even if there is free iova space available in the nodes
which are next to the cached node iova allocation can still fail
because of this approach.

Consider the following sequence of iova alloc and frees on
1GB of iova space

1) alloc - 500MB
2) alloc - 12MB
3) alloc - 499MB
4) free -  12MB which was allocated in step 2
5) alloc - 13MB

After the above sequence we will have 12MB of free iova space and
cached node will be pointing to the iova pfn of last alloc of 13MB
which will be the lowest iova pfn of that iova space. Now if we get an
alloc request of 2MB we just search from cached node and then look
for lower iova pfn's for free iova and as they aren't any, iova alloc
fails though there is 12MB of free iova space.

To avoid such iova search failures do a retry from the last rb tree node
when iova search fails, this will search the entire tree and get an iova
if its available.

Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
---
 drivers/iommu/iova.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 49fc01f..4e77116 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -184,8 +184,9 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	struct rb_node *curr, *prev;
 	struct iova *curr_iova;
 	unsigned long flags;
-	unsigned long new_pfn;
+	unsigned long new_pfn, low_pfn_new;
 	unsigned long align_mask = ~0UL;
+	unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
 
 	if (size_aligned)
 		align_mask <<= fls_long(size - 1);
@@ -198,15 +199,25 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 
 	curr = __get_cached_rbnode(iovad, limit_pfn);
 	curr_iova = rb_entry(curr, struct iova, node);
+	low_pfn_new = curr_iova->pfn_hi + 1;
+
+retry:
 	do {
-		limit_pfn = min(limit_pfn, curr_iova->pfn_lo);
-		new_pfn = (limit_pfn - size) & align_mask;
+		high_pfn = min(high_pfn, curr_iova->pfn_lo);
+		new_pfn = (high_pfn - size) & align_mask;
 		prev = curr;
 		curr = rb_prev(curr);
 		curr_iova = rb_entry(curr, struct iova, node);
-	} while (curr && new_pfn <= curr_iova->pfn_hi);
-
-	if (limit_pfn < size || new_pfn < iovad->start_pfn) {
+	} while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn);
+
+	if (high_pfn < size || new_pfn < low_pfn) {
+		if (low_pfn == iovad->start_pfn && low_pfn_new < limit_pfn) {
+			high_pfn = limit_pfn;
+			low_pfn = low_pfn_new;
+			curr = &iovad->anchor.node;
+			curr_iova = rb_entry(curr, struct iova, node);
+			goto retry;
+		}
 		iovad->max32_alloc_size = size;
 		goto iova32_full;
 	}
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
1.9.1

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^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2020-09-30  5:59 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-08-20 12:49 [PATCH v2 1/2] iommu/iova: Retry from last rb tree node if iova search fails vjitta
2020-08-20 12:49 ` [PATCH v2 2/2] iommu/iova: Free global iova rcache on iova alloc failure vjitta
2020-09-18 14:41   ` Robin Murphy
2020-09-28 12:41     ` Vijayanand Jitta
2020-09-30  5:59       ` Vijayanand Jitta
2020-08-28  7:31 ` [PATCH v2 1/2] iommu/iova: Retry from last rb tree node if iova search fails Vijayanand Jitta
2020-09-14  4:50   ` Vijayanand Jitta
2020-09-18  8:18     ` Joerg Roedel
2020-09-18 14:18 ` Robin Murphy
2020-09-30  5:48   ` Vijayanand Jitta

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