lkml.org 
[lkml]   [2022]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] iommu/iova: Free all CPU rcache for retry when iova alloc failure
From
On 2022-03-04 04:46, yf.wang--- via iommu wrote:
> From: Yunfei Wang <yf.wang@mediatek.com>
>
> In alloc_iova_fast function, if an iova alloc request fail,
> it will free the iova ranges present in the percpu iova
> rcaches and free global iova rcache and then retry, but
> flushing CPU iova rcaches only for each online CPU, which
> will cause incomplete rcache cleaning, and iova rcaches of
> not online CPU cannot be flushed, because iova rcaches may
> also lead to fragmentation of iova space, so the next retry
> action may still be fail.
>
> Based on the above, so need to flushing all iova rcaches
> for each possible CPU, use for_each_possible_cpu instead of
> for_each_online_cpu like in free_iova_rcaches function,
> so that all rcaches can be completely released to try
> replenishing IOVAs.

OK, so either there's a mystery bug where IOVAs somehow get freed on
offline CPUs, or the hotplug notifier isn't working correctly, or you've
contrived a situation where alloc_iova_fast() is actually racing against
iova_cpuhp_dead(). In the latter case, the solution is "don't do that".

This change should not be necessary.

Thanks,
Robin.

> Signed-off-by: Yunfei Wang <yf.wang@mediatek.com>
> Cc: <stable@vger.kernel.org> # 5.4.*
> ---
> drivers/iommu/iova.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index b28c9435b898..5a0637cd7bc2 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -460,7 +460,7 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
>
> /* Try replenishing IOVAs by flushing rcache. */
> flush_rcache = false;
> - for_each_online_cpu(cpu)
> + for_each_possible_cpu(cpu)
> free_cpu_cached_iovas(cpu, iovad);
> free_global_cached_iovas(iovad);
> goto retry;
>
>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

\
 
 \ /
  Last update: 2022-03-04 15:04    [W:0.104 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site