mm/hmm: properly take MMIO path

In case peer-to-peer transaction traverses through host bridge,
the IOMMU needs to have IOMMU_MMIO flag, together with skip of
CPU sync.

The latter was handled by provided DMA_ATTR_SKIP_CPU_SYNC flag,
but IOMMU flag was missed, due to assumption that such memory
can be treated as regular one.

Reuse newly introduced DMA attribute to properly take MMIO path.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/998251caf3f9d1a3f6f8205f1f494c707fb4d8fa.1757423202.git.leonro@nvidia.com

Author: rleon

mm/hmm.c

@@ -746,7 +746,7 @@ dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
 	case PCI_P2PDMA_MAP_NONE:
 		break;
 	case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
-		attrs |= DMA_ATTR_SKIP_CPU_SYNC;
+		attrs |= DMA_ATTR_MMIO;
 		pfns[idx] |= HMM_PFN_P2PDMA;
 		break;
 	case PCI_P2PDMA_MAP_BUS_ADDR:
@@ -776,7 +776,7 @@ dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
 			goto error;
 
 		dma_addr = dma_map_phys(dev, paddr, map->dma_entry_size,
-					DMA_BIDIRECTIONAL, 0);
+					DMA_BIDIRECTIONAL, attrs);
 		if (dma_mapping_error(dev, dma_addr))
 			goto error;
 
@@ -811,16 +811,17 @@ bool hmm_dma_unmap_pfn(struct device *dev, struct hmm_dma_map *map, size_t idx)
 	if ((pfns[idx] & valid_dma) != valid_dma)
 		return false;
 
+	if (pfns[idx] & HMM_PFN_P2PDMA)
+		attrs |= DMA_ATTR_MMIO;
+
 	if (pfns[idx] & HMM_PFN_P2PDMA_BUS)
 		; /* no need to unmap bus address P2P mappings */
-	else if (dma_use_iova(state)) {
-		if (pfns[idx] & HMM_PFN_P2PDMA)
-			attrs |= DMA_ATTR_SKIP_CPU_SYNC;
+	else if (dma_use_iova(state))
 		dma_iova_unlink(dev, state, idx * map->dma_entry_size,
 				map->dma_entry_size, DMA_BIDIRECTIONAL, attrs);
-	} else if (dma_need_unmap(dev))
+	else if (dma_need_unmap(dev))
 		dma_unmap_phys(dev, dma_addrs[idx], map->dma_entry_size,
-			       DMA_BIDIRECTIONAL, 0);
+			       DMA_BIDIRECTIONAL, attrs);
 
 	pfns[idx] &=
 		~(HMM_PFN_DMA_MAPPED | HMM_PFN_P2PDMA | HMM_PFN_P2PDMA_BUS);