Re: [PATCH v5 2/2] iommu/iova: Free global iova rcache on iova alloc failure

From: Robin Murphy
Date: Tue Nov 03 2020 - 07:35:25 EST


On 2020-09-30 08:44, vjitta@xxxxxxxxxxxxxx wrote:
From: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>

When ever an iova alloc request fails we free the iova
ranges present in the percpu iova rcaches and then retry
but the global iova rcache is not freed as a result we could
still see iova alloc failure even after retry as global
rcache is holding the iova's which can cause fragmentation.
So, free the global iova rcache as well and then go for the
retry.

This looks reasonable to me - it's mildly annoying that we end up with so many similar-looking functions, but the necessary differences are right down in the middle of the loops so nothing can reasonably be factored out :(

Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>

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

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index c3a1a8e..faf9b13 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -25,6 +25,7 @@ static void init_iova_rcaches(struct iova_domain *iovad);
static void free_iova_rcaches(struct iova_domain *iovad);
static void fq_destroy_all_entries(struct iova_domain *iovad);
static void fq_flush_timeout(struct timer_list *t);
+static void free_global_cached_iovas(struct iova_domain *iovad);
void
init_iova_domain(struct iova_domain *iovad, unsigned long granule,
@@ -442,6 +443,7 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
flush_rcache = false;
for_each_online_cpu(cpu)
free_cpu_cached_iovas(cpu, iovad);
+ free_global_cached_iovas(iovad);
goto retry;
}
@@ -1057,5 +1059,26 @@ void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad)
}
}
+/*
+ * free all the IOVA ranges of global cache
+ */
+static void free_global_cached_iovas(struct iova_domain *iovad)
+{
+ struct iova_rcache *rcache;
+ unsigned long flags;
+ int i, j;
+
+ for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
+ rcache = &iovad->rcaches[i];
+ spin_lock_irqsave(&rcache->lock, flags);
+ for (j = 0; j < rcache->depot_size; ++j) {
+ iova_magazine_free_pfns(rcache->depot[j], iovad);
+ iova_magazine_free(rcache->depot[j]);
+ rcache->depot[j] = NULL;
+ }
+ rcache->depot_size = 0;
+ spin_unlock_irqrestore(&rcache->lock, flags);
+ }
+}
MODULE_AUTHOR("Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>");
MODULE_LICENSE("GPL");