Re: [PATCH v2 3/7] s390/pci: Use dma-iommu layer

Robin Murphy
2022-11-28T18:20:01Z

On 2022-11-16 17:16, Niklas Schnelle wrote:
[...]
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index dc5f7a156ff5..804fb8f42d61 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -93,7 +93,7 @@ config IOMMU_DEBUGFS
> choice
> prompt "IOMMU default domain type"
> depends on IOMMU_API
> - default IOMMU_DEFAULT_DMA_LAZY if X86 || IA64
> + default IOMMU_DEFAULT_DMA_LAZY if X86 || IA64 || S390
> default IOMMU_DEFAULT_DMA_STRICT
> help
> Choose the type of IOMMU domain used to manage DMA API usage by
> @@ -412,6 +412,7 @@ config ARM_SMMU_V3_SVA
> config S390_IOMMU
> def_bool y if S390 && PCI
> depends on S390 && PCI
> + select IOMMU_DMA

Please add S390 to the condition under config IOMMU_DMA instead.

> select IOMMU_API
> help
> Support for the IOMMU API for s390 PCI devices.
[...]
> @@ -45,9 +329,14 @@ static struct iommu_domain *s390_domain_alloc(unsigned domain_type)
> {
> struct s390_domain *s390_domain;
>
> - if (domain_type != IOMMU_DOMAIN_UNMANAGED)
> + switch (domain_type) {
> + case IOMMU_DOMAIN_DMA:
> + case IOMMU_DOMAIN_DMA_FQ:

I was about to question adding this without any visible treatment of
iommu_iotlb_gather_queued() or domain->type == IOMMU_DOMAIN_DMA_FQ as a
whole, but I guess if you never actually free any pagetables it does
work out OK. Bit of a timebomb if there's a chance of that ever changing
in future, though.

> + case IOMMU_DOMAIN_UNMANAGED:
> + break;
> + default:
> return NULL;
> -
> + }
> s390_domain = kzalloc(sizeof(*s390_domain), GFP_KERNEL);
> if (!s390_domain)
> return NULL;
[...]
> @@ -397,12 +678,29 @@ static size_t s390_iommu_unmap_pages(struct iommu_domain *domain,
> return 0;
>
> iommu_iotlb_gather_add_range(gather, iova, size);
> + atomic64_add(pgcount, &s390_domain->ctrs.unmapped_pages);
>
> return size;
> }
>
> +static void s390_iommu_probe_finalize(struct device *dev)
> +{
> + struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> +
> + iommu_dma_forcedac = true;
> + iommu_setup_dma_ops(dev, domain->geometry.aperture_start, domain->geometry.aperture_end);

For consistency with all but one other caller now, just pass 0 and
U64_MAX for base and size to make it clear that they're meaningless
(they will eventually go away as part of a bigger refactoring).

Thanks,
Robin.