Re: [PATCH v3 2/4] iommu/io-pgtable-arm: Add read_and_clear_dirty() support

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, May 22, 2024 at 07:12:27AM +0000, Tian, Kevin wrote:
> > +static int arm_lpae_read_and_clear_dirty(struct io_pgtable_ops *ops,
> > +					 unsigned long iova, size_t size,
> > +					 unsigned long flags,
> > +					 struct iommu_dirty_bitmap *dirty)
> > +{
> > +	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
> > +	struct io_pgtable_cfg *cfg = &data->iop.cfg;
> > +	struct io_pgtable_walk_data walk_data = {
> > +		.dirty = dirty,
> > +		.flags = flags,
> > +		.addr = iova,
> > +		.end = iova + size,
> > +	};
> > +	arm_lpae_iopte *ptep = data->pgd;
> > +	int lvl = data->start_level;
> > +
> > +	if (WARN_ON(!size))
> > +		return -EINVAL;
> > +	if (WARN_ON((iova + size - 1) & ~(BIT(cfg->ias) - 1)))
> > +		return -EINVAL;
> > +	if (data->iop.fmt != ARM_64_LPAE_S1)
> > +		return -EINVAL;
> > +
> > +	return __arm_lpae_iopte_walk_dirty(data, &walk_data, ptep, lvl);
> 
> Intel/AMD drivers also checks:
> 
>         if (!dmar_domain->dirty_tracking && dirty->bitmap)
>                 return -EINVAL;

Those both seem redundant checks on a fast path?

Jason