Messages in this thread | | | Date | Wed, 8 Dec 2021 09:13:58 -0400 | From | Jason Gunthorpe <> | Subject | Re: [PATCH 4/4] dmaengine: idxd: Use DMA API for in-kernel DMA with PASID |
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On Tue, Dec 07, 2021 at 05:47:14AM -0800, Jacob Pan wrote: > In-kernel DMA should be managed by DMA mapping API. The existing kernel > PASID support is based on the SVA machinery in SVA lib that is intended > for user process SVA. The binding between a kernel PASID and kernel > mapping has many flaws. See discussions in the link below. > > This patch utilizes iommu_enable_pasid_dma() to enable DSA to perform DMA > requests with PASID under the same mapping managed by DMA mapping API. > In addition, SVA-related bits for kernel DMA are removed. As a result, > DSA users shall use DMA mapping API to obtain DMA handles instead of > using kernel virtual addresses.
Er, shouldn't this be adding dma_map/etc type calls?
You can't really say a driver is using the DMA API without actually calling the DMA API..
> + /* > + * Try to enable both in-kernel and user DMA request with PASID. > + * PASID is supported unless both user and kernel PASID are > + * supported. Do not fail probe here in that idxd can still be > + * used w/o PASID or IOMMU. > + */ > + if (iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) || > + idxd_enable_system_pasid(idxd)) { > + dev_warn(dev, "Failed to enable PASID\n"); > + } else { > + set_bit(IDXD_FLAG_PASID_ENABLED, &idxd->flags); > }
Huh? How can the driver keep going if PASID isn't supported? I thought the whole point of this was because the device cannot do DMA without PASID at all?
Jason
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