Messages in this thread | | | Date | Wed, 8 Dec 2021 10:49:39 -0800 | From | Jacob Pan <> | Subject | Re: [PATCH 2/4] iommu: Add PASID support for DMA mapping API users |
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Hi Lu,
On Wed, 8 Dec 2021 10:31:36 +0800, Lu Baolu <baolu.lu@linux.intel.com> wrote:
> Hi Jacob, > > On 12/7/21 9:47 PM, Jacob Pan wrote: > > DMA mapping API is the de facto standard for in-kernel DMA. It operates > > on a per device/RID basis which is not PASID-aware. > > > > Some modern devices such as Intel Data Streaming Accelerator, PASID is > > required for certain work submissions. To allow such devices use DMA > > mapping API, we need the following functionalities: > > 1. Provide device a way to retrieve a kernel PASID for work submission > > 2. Enable the kernel PASID on the IOMMU > > 3. Establish address space for the kernel PASID that matches the default > > domain. Let it be IOVA or physical address in case of pass-through. > > > > This patch introduces a driver facing API that enables DMA API > > PASID usage. Once enabled, device drivers can continue to use DMA APIs > > as is. There is no difference in dma_handle between without PASID and > > with PASID. > > Can a device issue DMA requests with PASID even there's no system IOMMU > or the system IOMMU is disabled? > Good point. If IOMMU is not enabled, device cannot issue DMA requests with PASID. This API will not be available. Forgot to add dummy functions to the header.
> Best regards, > baolu
Thanks,
Jacob
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