Re: [PATCH v3 01/10] iommu: Add helper to get minimal page size of domain

[Lu Baolu]

Hi Robin,

On 4/29/19 6:55 PM, Robin Murphy wrote:
> On 21/04/2019 02:17, Lu Baolu wrote:
> > This makes it possible for other modules to know the minimal
> > page size supported by a domain without the knowledge of the
> > structure details.
> >
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> > Â include/linux/iommu.h | 13 +++++++++++++
> > Â 1 file changed, 13 insertions(+)
> >
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index a5007d035218..46679ef19b7e 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -377,6 +377,14 @@ static inline void iommu_tlb_sync(struct 
> > iommu_domain *domain)
> > ÂÂÂÂÂÂÂÂÂ domain->ops->iotlb_sync(domain);
> > Â }
> > +static inline unsigned long domain_minimal_pgsize(struct iommu_domain 
> > *domain)
> > +{
> > +ÂÂÂ if (domain && domain->pgsize_bitmap)
> > +ÂÂÂÂÂÂÂ return 1 << __ffs(domain->pgsize_bitmap);
>
> Nit: this would probably be more efficient on most architectures as:
>
>  ÂÂÂÂif (domain)
>  ÂÂÂÂÂÂÂ return domain->pgsize_bitmap & -domain->pgsize_bitmap;

It looks reasonable to me.

> I'd also suggest s/minimal/min/ in the name, just to stop it getting too 
> long. Otherwise, though, I like the idea, and there's at least one other 
> place (in iommu-dma) that can make use of it straight away.

Okay, I will change the name to domain_min_pgsize().

> Robin.

Best regards,
Lu Baolu

> > +
> > +ÂÂÂ return 0;
> > +}
> > +
> > Â /* PCI device grouping function */
> > Â extern struct iommu_group *pci_device_group(struct device *dev);
> > Â /* Generic device grouping function */
> > @@ -704,6 +712,11 @@ const struct iommu_ops 
> > *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
> > ÂÂÂÂÂ return NULL;
> > Â }
> > +static inline unsigned long domain_minimal_pgsize(struct iommu_domain 
> > *domain)
> > +{
> > +ÂÂÂ return 0;
> > +}
> > +
> > Â #endif /* CONFIG_IOMMU_API */
> > Â #ifdef CONFIG_IOMMU_DEBUGFS