Re: [PATCH v6 17/25] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()

Jason Gunthorpe
2020-05-01T12:55:18Z

On Fri, May 01, 2020 at 05:15:52AM -0700, Christoph Hellwig wrote:
> > @@ -432,6 +432,7 @@ config ARM_SMMU_V3
> > tristate "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
> > depends on ARM64
> > select IOMMU_API
> > + select IOMMU_SVA
> > select IOMMU_IO_PGTABLE_LPAE
> > select GENERIC_MSI_IRQ_DOMAIN
>
> Doesn't this need to select MMU_NOTIFIER now?
>
> > + struct mmu_notifier_ops mn_ops;
>
> Note: not a pointer.
>
> > + /* If bind() was already called for this (dev, mm) pair, reuse it. */
> > + list_for_each_entry(bond, &master->bonds, list) {
> > + if (bond->mm == mm) {
> > + refcount_inc(&bond->refs);
> > + return &bond->sva;
> > + }
> > + }

I also would like it if searching for mms in linked lists was not
necessary, this is kind of the point of 'get'

Is this a side effect of the earlier remark to get rid of the linked
list inside the notifier?

> Or we could enhance the mmu_notifier_get to pass a private
> oaque instance ID pointer, which is checked in addition to the ops,
> and you could probably kill off the bonds list and lookup.

This might be the best option if it can absorb the above search..

Jason