Re: [PATCH v4 06/13] iommu/arm-smmu-v3: Add context descriptor tables allocators

[Will Deacon <will@kernel.org>]

On Tue, Jan 14, 2020 at 12:52:30PM +0100, Jean-Philippe Brucker wrote:
> On Tue, Jan 14, 2020 at 11:06:52AM +0000, Will Deacon wrote:
> > >  /* Context descriptor manipulation functions */
> > > +static int arm_smmu_alloc_cd_leaf_table(struct arm_smmu_device *smmu,
> > > +					struct arm_smmu_cd_table *table,
> > > +					size_t num_entries)
> > > +{
> > > +	size_t size = num_entries * (CTXDESC_CD_DWORDS << 3);
> > > +
> > > +	table->ptr = dmam_alloc_coherent(smmu->dev, size, &table->ptr_dma,
> > > +					 GFP_KERNEL);
> > > +	if (!table->ptr) {
> > > +		dev_warn(smmu->dev,
> > > +			 "failed to allocate context descriptor table\n");
> > > +		return -ENOMEM;
> > > +	}
> > > +	return 0;
> > > +}
> > > +
> > > +static void arm_smmu_free_cd_leaf_table(struct arm_smmu_device *smmu,
> > > +					struct arm_smmu_cd_table *table,
> > > +					size_t num_entries)
> > > +{
> > > +	size_t size = num_entries * (CTXDESC_CD_DWORDS << 3);
> > > +
> > > +	dmam_free_coherent(smmu->dev, size, table->ptr, table->ptr_dma);
> > > +}
> > 
> > I think we'd be better off taking the 'arm_smmu_s1_cfg' as a parameter here
> > instead of the table pointer and a num_entries value, since the code above
> > implies that we support partial freeing of the context descriptors.
> > 
> > I can do that as a follow-up patch if you agree. Thoughts?
> 
> Do you mean only changing the arguments of arm_smmu_free_cd_leaf_table(),
> or arm_smmu_alloc_cd_leaf_table() as well? For free() I agree, for alloc()
> I'm not sure it would look better.

Yeah, just for free(). I'll spin something on top after I've finished
reviewing the series.

> For my tests I have a debug patch that allocates PASIDs randomly which
> quickly consumes DMA for leaf tables. So I do have to free the leaves
> individually when they aren't used, but it will be easy for me to update.

Cool.

Will