Re: [RFC v1 0/3] Add VIRTIO_F_IOMMU_PLATFORM support

[Brijesh Singh <brijesh.singh@amd.com>]

Hi Andrew,

On 07/27/2017 04:38 PM, Andrew Fish wrote:
> 
> Brijesh,
> 
> If you look in the UEFI Spec 13.4 EFI PCI I/O Protocol there is a good write on DMA.
> 
> DMA Bus Master Read Operation
> =========================
> Call Map() for EfiPciIoOperationBusMasterRead.
> Program the DMA Bus Master with the DeviceAddress returned by Map(). Start the DMA Bus Master.
> Wait for DMA Bus Master to complete the read operation.
> Call Unmap().
> 
> 
> DMA Bus Master Write Operation
> ==========================
> Call Map() for EfiPciOperationBusMasterWrite.
> Program the DMA Bus Master with the DeviceAddress returned by Map().
> Start the DMA Bus Master.
> Wait for DMA Bus Master to complete the write operation.
> Perform a PCI controller specific read transaction to flush all PCI write buffers (See PCI Specification Section 3.2.5.2) .
> Call Flush().
> Call Unmap().
> 
> DMA Bus Master Common Buffer Operation
> ==================================
> Call AllocateBuffer() to allocate a common buffer.
> Call Map() for EfiPciIoOperationBusMasterCommonBuffer.
> Program the DMA Bus Master with the DeviceAddress returned by Map().
> The common buffer can now be accessed equally by the processor and the DMA bus master. Call Unmap().
> Call FreeBuffer().
> 

Thanks for the link.

-Brijesh