Re: [PATCH v3 2/4] dma-iommu: Add iommu_dma_opt_mapping_size()

[John Garry]

On 14/06/2022 14:12, John Garry wrote:
> On 06/06/2022 10:30, John Garry wrote:
> > Add the IOMMU callback for DMA mapping API dma_opt_mapping_size(), which
> > allows the drivers to know the optimal mapping limit and thus limit the
> > requested IOVA lengths.
> >
> > This value is based on the IOVA rcache range limit, as IOVAs allocated
> > above this limit must always be newly allocated, which may be quite slow.
>
> Can I please get some sort of ack from the IOMMU people on this one?

Another request for an ack please.

Thanks,
john

> > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> > Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/dma-iommu.c | 6 ++++++
> >   drivers/iommu/iova.c      | 5 +++++
> >   include/linux/iova.h      | 2 ++
> >   3 files changed, 13 insertions(+)
> >
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index f90251572a5d..9e1586447ee8 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -1459,6 +1459,11 @@ static unsigned long 
> > iommu_dma_get_merge_boundary(struct device *dev)
> >       return (1UL << __ffs(domain->pgsize_bitmap)) - 1;
> >   }
> > +static size_t iommu_dma_opt_mapping_size(void)
> > +{
> > +    return iova_rcache_range();
> > +}
> > +
> >   static const struct dma_map_ops iommu_dma_ops = {
> >       .alloc            = iommu_dma_alloc,
> >       .free            = iommu_dma_free,
> > @@ -1479,6 +1484,7 @@ static const struct dma_map_ops iommu_dma_ops = {
> >       .map_resource        = iommu_dma_map_resource,
> >       .unmap_resource        = iommu_dma_unmap_resource,
> >       .get_merge_boundary    = iommu_dma_get_merge_boundary,
> > +    .opt_mapping_size    = iommu_dma_opt_mapping_size,
> >   };
> >   /*
> > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> > index db77aa675145..9f00b58d546e 100644
> > --- a/drivers/iommu/iova.c
> > +++ b/drivers/iommu/iova.c
> > @@ -26,6 +26,11 @@ static unsigned long iova_rcache_get(struct 
> > iova_domain *iovad,
> >   static void free_cpu_cached_iovas(unsigned int cpu, struct 
> > iova_domain *iovad);
> >   static void free_iova_rcaches(struct iova_domain *iovad);
> > +unsigned long iova_rcache_range(void)
> > +{
> > +    return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1);
> > +}
> > +
> >   static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node)
> >   {
> >       struct iova_domain *iovad;
> > diff --git a/include/linux/iova.h b/include/linux/iova.h
> > index 320a70e40233..c6ba6d95d79c 100644
> > --- a/include/linux/iova.h
> > +++ b/include/linux/iova.h
> > @@ -79,6 +79,8 @@ static inline unsigned long iova_pfn(struct 
> > iova_domain *iovad, dma_addr_t iova)
> >   int iova_cache_get(void);
> >   void iova_cache_put(void);
> > +unsigned long iova_rcache_range(void);
> > +
> >   void free_iova(struct iova_domain *iovad, unsigned long pfn);
> >   void __free_iova(struct iova_domain *iovad, struct iova *iova);
> >   struct iova *alloc_iova(struct iova_domain *iovad, unsigned long size,