Re: [PATCH v7 2/9] ACPI/IORT: Add support for RMR node parsing

[Laurentiu Tudor <laurentiu.tudor@nxp.com>]

On 8/5/2021 7:03 PM, Lorenzo Pieralisi wrote:
> On Thu, Aug 05, 2021 at 09:07:17AM +0100, Shameer Kolothum wrote:
> 
> [...]
> 
>> +static void __init iort_node_get_rmr_info(struct acpi_iort_node *iort_node)
>> +{
>> +	struct acpi_iort_node *smmu;
>> +	struct acpi_iort_rmr *rmr;
>> +	struct acpi_iort_rmr_desc *rmr_desc;
>> +	u32 map_count = iort_node->mapping_count;
>> +	u32 sid;
>> +	int i;
>> +
>> +	if (!iort_node->mapping_offset || map_count != 1) {
>> +		pr_err(FW_BUG "Invalid ID mapping, skipping RMR node %p\n",
>> +		       iort_node);
>> +		return;
>> +	}
>> +
>> +	/* Retrieve associated smmu and stream id */
>> +	smmu = iort_node_get_id(iort_node, &sid, 0);
>> +	if (!smmu) {
>> +		pr_err(FW_BUG "Invalid SMMU reference, skipping RMR node %p\n",
>> +		       iort_node);
>> +		return;
>> +	}
>> +
>> +	/* Retrieve RMR data */
>> +	rmr = (struct acpi_iort_rmr *)iort_node->node_data;
>> +	if (!rmr->rmr_offset || !rmr->rmr_count) {
>> +		pr_err(FW_BUG "Invalid RMR descriptor array, skipping RMR node %p\n",
>> +		       iort_node);
>> +		return;
>> +	}
>> +
>> +	rmr_desc = ACPI_ADD_PTR(struct acpi_iort_rmr_desc, iort_node,
>> +				rmr->rmr_offset);
>> +
>> +	iort_rmr_desc_check_overlap(rmr_desc, rmr->rmr_count);
>> +
>> +	for (i = 0; i < rmr->rmr_count; i++, rmr_desc++) {
>> +		struct iommu_resv_region *region;
>> +		enum iommu_resv_type type;
>> +		int prot = IOMMU_READ | IOMMU_WRITE;
>> +		u64 addr = rmr_desc->base_address, size = rmr_desc->length;
>> +
>> +		if (!IS_ALIGNED(addr, SZ_64K) || !IS_ALIGNED(size, SZ_64K)) {
>> +			/* PAGE align base addr and size */
>> +			addr &= PAGE_MASK;
>> +			size = PAGE_ALIGN(size + offset_in_page(rmr_desc->base_address));
>> +
>> +			pr_err(FW_BUG "RMR descriptor[0x%llx - 0x%llx] not aligned to 64K, continue with [0x%llx - 0x%llx]\n",
>> +			       rmr_desc->base_address,
>> +			       rmr_desc->base_address + rmr_desc->length - 1,
>> +			       addr, addr + size - 1);
>> +		}
>> +		if (rmr->flags & IOMMU_RMR_REMAP_PERMITTED) {
>> +			type = IOMMU_RESV_DIRECT_RELAXABLE;
>> +			/*
>> +			 * Set IOMMU_CACHE as IOMMU_RESV_DIRECT_RELAXABLE is
>> +			 * normally used for allocated system memory that is
>> +			 * then used for device specific reserved regions.
>> +			 */
>> +			prot |= IOMMU_CACHE;
>> +		} else {
>> +			type = IOMMU_RESV_DIRECT;
>> +			/*
>> +			 * Set IOMMU_MMIO as IOMMU_RESV_DIRECT is normally used
>> +			 * for device memory like MSI doorbell.
>> +			 */
>> +			prot |= IOMMU_MMIO;
>> +		}
> 
> On the prot value assignment based on the remapping flag, I'd like to
> hear Robin/Joerg's opinion, I'd avoid being in a situation where
> "normally" this would work but then we have to quirk it.
> 
> Is this a valid assumption _always_ ?

I think we enable quite a bit of platforms with this assumption, so IMHO
it's a fair compromise for now. As per Jon's comment and oob
discussions, in the long run the spec should probably be updated to
include a way of explicitly specifying memory attributes.

---
Thanks & Best Regards, Laurentiu

> 
>> +
>> +		region = iommu_alloc_resv_region(addr, size, prot, type);
>> +		if (region) {
>> +			region->fw_data.rmr.flags = rmr->flags;
>> +			region->fw_data.rmr.sid = sid;
>> +			region->fw_data.rmr.smmu = smmu;
>> +			list_add_tail(&region->list, &iort_rmr_list);
>> +		}
>> +	}
>> +}
>> +
>> +static void __init iort_parse_rmr(void)
>> +{
>> +	struct acpi_iort_node *iort_node, *iort_end;
>> +	struct acpi_table_iort *iort;
>> +	int i;
>> +
>> +	if (iort_table->revision < 3)
>> +		return;
>> +
>> +	iort = (struct acpi_table_iort *)iort_table;
>> +
>> +	iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort,
>> +				 iort->node_offset);
>> +	iort_end = ACPI_ADD_PTR(struct acpi_iort_node, iort,
>> +				iort_table->length);
>> +
>> +	for (i = 0; i < iort->node_count; i++) {
>> +		if (WARN_TAINT(iort_node >= iort_end, TAINT_FIRMWARE_WORKAROUND,
>> +			       "IORT node pointer overflows, bad table!\n"))
>> +			return;
>> +
>> +		if (iort_node->type == ACPI_IORT_NODE_RMR)
>> +			iort_node_get_rmr_info(iort_node);
>> +
>> +		iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,
>> +					 iort_node->length);
>> +	}
>> +}
>>  
>>  static void __init iort_init_platform_devices(void)
>>  {
>> @@ -1636,6 +1767,7 @@ void __init acpi_iort_init(void)
>>  	}
>>  
>>  	iort_init_platform_devices();
>> +	iort_parse_rmr();
>>  }
>>  
>>  #ifdef CONFIG_ZONE_DMA
>> -- 
>> 2.17.1
>>
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