RE: [PATCH 3/5] iommu/arm-smmu-v3: Add read_and_clear_dirty() support

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Wednesday, November 29, 2023 7:35 PM
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> Cc: iommu@lists.linux.dev; linux-arm-kernel@lists.infradead.org;
> robin.murphy@arm.com; will@kernel.org; joro@8bytes.org;
> kevin.tian@intel.com; nicolinc@nvidia.com; mshavit@google.com;
> eric.auger@redhat.com; joao.m.martins@oracle.com; jiangkunkun
> <jiangkunkun@huawei.com>; zhukeqian <zhukeqian1@huawei.com>; Linuxarm
> <linuxarm@huawei.com>
> Subject: Re: [PATCH 3/5] iommu/arm-smmu-v3: Add read_and_clear_dirty()
> support
> 
> On Tue, Nov 28, 2023 at 09:49:38AM +0000, Shameer Kolothum wrote:
> 
> > +static int arm_smmu_read_and_clear_dirty(struct iommu_domain *domain,
> > +					 unsigned long iova, size_t size,
> > +					 unsigned long flags,
> > +					 struct iommu_dirty_bitmap *dirty)
> > +{
> > +	struct arm_smmu_domain *smmu_domain =
> to_smmu_domain(domain);
> > +	struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
> > +	int ret;
> > +
> > +	if (smmu_domain->stage != ARM_SMMU_DOMAIN_S1)
> > +		return -EINVAL;
> > +
> > +	if (!ops || !ops->read_and_clear_dirty) {
> > +		pr_err_once("io-pgtable don't support dirty tracking\n");
> > +		return -ENODEV;
> 
> All these prints concern me, either these can never happen due to
> constraints on the caller, eg iommufd, in which case use WARN_ON_ONCe
> 
> Or iommufd does allow these improper things and thus it should
> silently fail.
> 
Ok. Will revisit these for next revision.

Thanks,
Shameer