IOMMU Remapping Functions

These functions are intended for IOMMU remapping operations.

All IOMMU remapping function definitions are located in: $ICP_ROOT/quickassist/lookaside/access_layer/include/icp_sal_iommu.h

icp_sal_iommu_get_remap_size

Returns the page_size rounded for IOMMU remapping.

Syntax

size_t icp_sal_iommu_get_remap_size(size_t size);

Parameters

size	The minimum required page size.

Return Value

The icp_sal_iommu_get_remap_size function returns the page_size rounded for IOMMU remapping.

icp_sal_iommu_map

Adds an entry to the IOMMU remapping table.

Syntax

CpaStatus icp_sal_iommu_map(Cpa64U phaddr, Cpa64U iova, size_t size);

Parameters

phaddr	Host physical address.
iova	Guest physical address.
size	Size of the remapped region.

Return Value

The icp_sal_iommu_map function returns one of the following codes:

CPA_STATUS_SUCCESS	Successful operation.
CPA_STATUS_FAIL	Indicates a failure.

icp_sal_iommu_unmap

Removes an entry from the IOMMU remapping table.

Syntax

CpaStatus icp_sal_iommu_unmap(Cpa64U iova, size_t size);

Parameters

iova	Guest physical address.
size	Size of the remapped region.

Return Value

The icp_sal_iommu_unmap function returns one of the following codes:

CPA_STATUS_SUCCESS	Successful operation.
CPA_STATUS_FAIL	Indicates a failure.

IOMMU Remapping Function Usage

These functions are required when the user wants to access an acceleration service from the Physical Function (PF) when SR-IOV is enabled in the driver. In this case, all I/O transactions from the device go through DMA remapping hardware.

This hardware checks:

1. If the transaction is legitimate

2. What physical address the given I/O address needs to be translated to.

If the I/O address is not in the transaction table, it fails with a DMA Read error shown as follows:

• DRHD: Handling fault status reg 3.

• DMAR:[DMA Read] Request device [02:01.2] fault addr <ADDR> DMAR:[fault reason 06] PTE Read access is not set.

To make this work, the user must add a 1:1 mapping as follows:

1. Get the size required for a buffer.

   int size = icp_sal_iommu_get_remap_size(size_of_data);

2. Allocate a buffer.

   char *buff = malloc(size);

3. Get a physical pointer to the buffer.

   buff_phys_addr = virt_to_phys(buff);

4. Add a 1:1 mapping to the IOMMU tables.

   icp_sal_iommu_map(buff_phys_addr, buff_phys_addr, size;

5. Use the buffer to send data to the Intel^® QAT Endpoint.

6. Before freeing the buffer, remove the IOMMU table entry.

   icp_sal_iommu_unmap(buff_phys_addr, size);

7. Free the buffer.

   free(buff);

The IOMMU remapping functions can be used in all contexts that the Intel^® QAT APIs can be used, that is, kernel and user space in a Physical Function (PF) Domain 0, as well as kernel and user space in a Virtual Machine (VM).

In the case of VM, the APIs will do nothing. In the PF Domain 0 case, the APIs will update the hardware IOMMU tables.