Re: [PATCH v3 7/8] arm64: mm: Set ZONE_DMA size based on early IORT scan

[Lorenzo Pieralisi]

On Wed, Oct 14, 2020 at 09:12:09PM +0200, Nicolas Saenz Julienne wrote:

[...]

> +unsigned int __init acpi_iort_get_zone_dma_size(void)
> +{
> +	struct acpi_table_iort *iort;
> +	struct acpi_iort_node *node, *end;
> +	acpi_status status;
> +	u8 limit = 32;
> +	int i;
> +
> +	if (acpi_disabled)
> +		return limit;
> +
> +	status = acpi_get_table(ACPI_SIG_IORT, 0,
> +				(struct acpi_table_header **)&iort);
> +	if (ACPI_FAILURE(status))
> +		return limit;
> +
> +	node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset);
> +	end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length);
> +
> +	for (i = 0; i < iort->node_count; i++) {
> +		if (node >= end)
> +			break;
> +
> +		switch (node->type) {
> +			struct acpi_iort_named_component *ncomp;
> +			struct acpi_iort_root_complex *rc;
> +
> +		case ACPI_IORT_NODE_NAMED_COMPONENT:
> +			ncomp = (struct acpi_iort_named_component *)node->node_data;
> +			if (ncomp->memory_address_limit)
> +				limit = min(limit, ncomp->memory_address_limit);
> +			break;
> +
> +		case ACPI_IORT_NODE_PCI_ROOT_COMPLEX:
> +			rc = (struct acpi_iort_root_complex *)node->node_data;
> +			if (rc->memory_address_limit)

You need to add a node revision check here, see rc_dma_get_range() in
drivers/acpi/arm64/iort.c, otherwise we may be reading junk data
in older IORT tables - acpica structures are always referring to the
latest specs.

Thanks,
Lorenzo

> +				limit = min(limit, rc->memory_address_limit);
> +			break;
> +		}
> +		node = ACPI_ADD_PTR(struct acpi_iort_node, node, node->length);
> +	}
> +	acpi_put_table(&iort->header);
> +	return limit;
> +}
> +#endif
> diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
> index 20a32120bb88..7d2e184f0d4d 100644
> --- a/include/linux/acpi_iort.h
> +++ b/include/linux/acpi_iort.h
> @@ -38,6 +38,7 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *size);
>  const struct iommu_ops *iort_iommu_configure_id(struct device *dev,
>  						const u32 *id_in);
>  int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head);
> +unsigned int acpi_iort_get_zone_dma_size(void);
>  #else
>  static inline void acpi_iort_init(void) { }
>  static inline u32 iort_msi_map_id(struct device *dev, u32 id)
> @@ -55,6 +56,9 @@ static inline const struct iommu_ops *iort_iommu_configure_id(
>  static inline
>  int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head)
>  { return 0; }
> +
> +static inline unsigned int acpi_iort_get_zone_dma_size(void)
> +{ return 32; }
>  #endif
>  
>  #endif /* __ACPI_IORT_H__ */
> -- 
> 2.28.0
>