On 9/30/2020 1:14 PM, vji...@codeaurora.org wrote:
> From: Vijayanand Jitta
>
> 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
> Reviewed-by: Robin Murphy
> ---
> 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 30d969a..c3a1a8e 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, retry_pfn;
> 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);
> + retry_pfn = 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 && retry_pfn < limit_pfn) {
> + high_pfn = limit_pfn;
> + low_pfn = retry_pfn;
> + curr = >anchor.node;
> + curr_iova = rb_entry(curr, struct iova, node);
> + goto retry;
> + }
> iovad->max32_alloc_size = size;
> goto iova32_full;
> }
>
Gentle ping.
Thanks,
Vijay
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of Code Aurora Forum, hosted by The Linux Foundation
___
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
