Messages in this thread | | | Date | Fri, 4 Mar 2022 14:03:22 +0000 | Subject | Re: [PATCH] iommu/iova: Free all CPU rcache for retry when iova alloc failure | From | Robin Murphy <> |
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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
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